The Grim Adventures of Billy & Mandy VS Strategy Guide

 

Halloween is less than 10 days away and you all came back for the 4th week of Monster Month! Today we got something special for you. Over the years there have been plenty of Horror Cartoons; Courage the Cowardly Dog, Edgar & Ellen, Beetlejuice, Making Fiends, Aaahh!! Real Monsters, Invader Zim, Ruby Gloom and Many More. But none of them are nearly as large, powerful or influential as The Grim Adventures of Billy & Mandy! Beginning as a Hybrid show with Evil Con Carne called Grim & Evil in 2001, Billy & Mandy was created by Maxwell Atoms and was easily one of Cartoon Network's best shows throughout the 00s, attaining 7 seasons of television, movies, 2 different spin-offs, crossover specials, comics and videogames. On top of all that it also is easily one of the strongest cartoons ever made from a VS perspective, possibly at the top! How does one become OP here? Well stay tuned and I’ll tell you!

Island Tier:

So this is the tier of the ‘normal’ human and low tier monster characters of Billy and Mandy, including Billy & Mandy themselves, humankind, the Evil Con Carne cast, and the majority of Episodic Villains. The Town of Endsville is a mysterious place where strange things happen, existing at the edge of the world, it is a hotspot for all sorts of supernatural mischief great and small. Characters in this tier are Large Island level, due to feats such as every human in Endsville effortlessly tanking Grim’s guitar solo that obliterated the city, causing a massive earthquake and vaporizing all the buildings. Similarly the Evil Con Carne cast has effortlessly tanked the entirety of Bunny Island exploding with them in the center, multiple times. These two series exist in the same universe, and the humans have shown to be at a similar tier. As far as speed goes, Mandy was super casually able to react to and process Nergal’s tentacles as they pulled her to the Earth’s core at speeds of over Mach 3,000, and later in the show Billy as able to dodge around Hoss Delgado’s electric lightning shock, which travels through the air at nearly Mach 300,000, which would put characters here at Relativistic speed.

Even total civilian characters in this series are intelligent enough to build advanced vehicles and invent an energy source that can power an entire city for 3 weeks using only a drop of water. The more intelligent scientist characters like Major Doctor Ghastly, can invent weapons capable of blowing up the moon and even Time Travel, technically making Billy & Mandy a Level 3 society on the Kardashev Scale. Beyond that civilians can (somewhat inconsistently) breathe and survive in the vacuum of Space, and everyone on Earth is capable of Possessing people or animals, just by jumping into their heads, including Billy. Billy is the least intelligent character in the series, and possibly any cartoon going by feats, as he was able to score a -5 on a test even inanimate objects could score a 17 on. This might sound like an enormous disadvantage, but Billy’s quite literal lack of a brain has allowed him to blissfully do some incredibly impressive things sheerly due to lack of awareness. He can hold his breath for literal days on end, achieved spiritual enlightenment, ate a Kaiju-sized candy monster, and was unable to be manipulated by the Goddess of Chaos, Eris, and in fact made her suffer a panic attack as a result. Billy can melt creatures alive with his burps, instantly regenerate from being sliced to pieces or having his head explode, and can even move through Metafictional Space, such as when he and Grim were talking on the phone on a split screen, and Grim hung up the phone making Billy’s side pan off screen, but Billy himself remained static and ended up being teleported to Grim's location. For an example of a more competent human, look no further than Hoss Delgado, the local Spectral Exterminator with a bionic arm, he's been Bitten by Ghosts, Haunted by MoleRats and Slapped by Vampires. Hoss is an incredibly skilled badass fighter who can track sources and levels of supernatural power and has a massive arsenal of weapons to pull from, including a shotgun, netgun, shuriken launcher, grenade launcher, a cannon, a lightsaber, laser beam, electrical shocker, tractor beam, ectoplasmic goo strong enough to restrain Grim, and a crossbow that shoots chainsaws! The Wizards of Toadblatt’s School of Sorcery have numerous useful spells, such as turning invisible, transmutating foes into animals, generating dragons, forcing people to fall in love, and summoning others to them through the toilet. The Dark Wizard, Lord Moldybutt also has a curse on his name where if anyone dare says it it will destroy everything around them and gets more potent every time it is said. But let’s talk monsters, even basic Imps are capable of interdimensional travel and entities like The Great Snake, Shnissugah and Daisy the Chupacabra can even use immersion and travel through cyberspace and Television singles. You’ve got Logia slime monsters, Brain Eating Alien Meteors and Voodoo style Zombies who can control and animate any small piece of themselves and even merge together into some Zombie Kaiju monster that would make a SICK Resident Evil Boss Fight. There are numerous intangible ghosts in this tier, including Mrs. Doolin who can cast insane illusions, The Duck who is invisible and inaudible  to everyone but his current victim, and The Spirit of Pittsburg, who can haunt and control objects, regenerate, manipulate lightning, and create pocket dimensions. Skarr, after becoming one with his garden, can manipulate plant life and regenerate from being mulched, and Mindy is a powerful Witch who can induce sleep, bolster stats, and use numerous other spells. This tier also includes Pandora, an immortal girl who carries around the cursed box, if she can trick someone into opening it, it would end the world unleashing untold suffering and plagues on humanity, not to mention The Abominable Snowman, who is clearly the trickiest and most manipulative character in the entire show, able to cheat literal death for centuries. There are several other creatures in this tier, from traditional monsters like Werewolves, Giant Spiders and Phoenix’s which have all the classic powers you’d expect, to extremely unconventional ones like Snails with advanced Probability Manipulation good enough to make someone get struck by lightning 20 back to back times, a monster that has the power to ‘turn all other monsters into toast’ and Uncle Chokey’s Sentient Record Player, which can metafictionally change everything around it into a classic rubber hose cartoon with its music. But enough stalling, there is one Extreme threat in this tier we still have to address, terrifying beyond anything mentioned above, sits Mandy herself. Mandy is faster, stronger and Smarter than basically every other civilian character in the series, she is a master martial artist who can defeat entire armies of giant spiders in hand to hand combat, and bested Mrs. Doolin in fencing, and Mrs. Doolin was a world class Fencer who managed to defeat Grim and indefinitely delay her own death out of sheer skill. She was able to take control of the global spanning Kids Next Door organization and later escaped them by building rockets into her hair, and at the end of the series, took over as President of the Earth and in only a single Day led the world to defeat an Underworld invasion. But Mandy also possesses an unknown factor to her, her dark and mysterious powers. No one knows just where Mandy gets her dark powers from, but it has made her one of the most intimidating forces in the series, she was able to make General Skarr surrender Grim’s scythe to her with her mere presence, and with a mere glance, terrified a sentient mask designed by the top Underworld scientists to so horrifying it would scare the life out of anyone who sees it in an instant. Mandy is able to control Minds on a planet wide scale, casually making everyone on Earth do her bidding with a thought, and was able to kill and assimilate the Brain Meteor when it stole her brain. Her resistance to Mind Manipulation is just as impressive, seen most famously when The Delightful Reaper was Assimilating everyone in Cartoon Network, with all of them being merged into its Hive Mind, and Mandy stopped it by allowing herself to be assimilated, where she instantaneously took complete mental control over the creature, making it an extension of her rather than the other way around. She once casually froze time for everyone on the entire planet and later was also able to tell when Billy was rewinding her in time and Stopped him, she even seems to have some manipulation of Space, as shown when she somehow ate an entire City Dump….don’t ask. Mandy can teleport, manipulate fire, levitate, use telekinesis, summon ghosts from her mouth, make dimensional portals, has a passive good luck aura and has extreme levels of Metafictional Manipulation, one time even literally climbing out of the cartoon and watching it from outside their universe when she didn’t like the plot. She wears a ring that allows her to summon and control vast and horrible armies of the undead, and stole Ms. Slithers Yardstick that allows her to create anything she can imagine. Mandy seems to draw all these powers from her Nerve, her dark rebellious aura of the unknown related to her extreme levels of Scorpio energy. This Nerve has some insane feats, like the time Mandy met herself trom the Shadow Dimension, ones Shadow Self being everything that they are not, exactly the equal and opposite in every way, yet Mandy’s evil was still able to Break this shadow into being Exactly like Mandy. Mandy’s Nerve is so strong that one time Billy and Grim Removed her Nerve itself and had it become its own entity, yet Mandy was STILL able to beat her own Nerve with her Nerve. Her Nerve is so strong, she was able to use it to resist the Tooth Fairies Transmutation, which even Grim Feared, and resisted the Duck’s Humiliation abilities so thoroughly that it caused him to literally fade out of existence. But if all that fails there is one more thing to worry about with Mandy, you see, it is commonly pointed out in universe that Mandy Never Smiles. As it turns out, that is literally an absolute Law of reality, and Mandy breaking this is an ultimate Taboo. Should Mandy force herself to smile, it will literally Destroy and Rewrite Reality on a Multiversal Scale, as in this wouldn’t affect just The Grim Adventures of Billy & Mandy but ALL OF CARTOON NETWORK as a whole!

So as one can see the addition of Mandy really made this verse step up its game, but what would some effective strategies be to dominate this tier? So ignoring Mandy for a second, the cast of Billy & Mandy is often portrayed as being pretty Naïve, despite their intelligence, managing to manipulate them or build up one’s forces behind their back was always presented as super easy for villains to accomplish and generally only Mandy and Grim know totally what’s going on. Similarly most of these characters are incompetent in some way and end up failing in their goals whether they are hero’s or villains due to the fact Billy & Mandy has such a heavy theme of Balance, so anyone who tries to shake things up seems almost destiny bound to fail. This can even be seen with Mandy, who claims she never loses or fails, and while that is technically true, Mandy doesn’t really try and take over the world much, being mostly apathetic to things she doesn’t like and doing normal day to day things, as if aware of this Balance and is simply biding her time until she figures out a way around it. But how do you Stop Mandy? Well Mandy has been bested before but normally by things Far outside of her Tier, like when Grim’s Scythe mind controlled her or when transmutated by Eris or the Mask of the Beast, or when Horror’s Hand fear haxed her, despite her having really good resistance to those things. But there Are various powers Mandy has no counter play to at all. Characters in Billy and Mandy are quite susceptible to Age Manipulation, with even Mandy being helpless to stop herself from being aged backwards into nothingness. Despite Mandy having extremely strong Mental Defenses, this has done nothing to protect her from Possession, with even Billy managing to possess Mandy for days. And one of the most consistent ways to stop Mandy is via sealing, Mandy’s only counterplay to being sealed in a dimension without Grim is to attempt to carve a dimensional portal, which is difficult to do without supplies. Probably the most damning thing about Mandy is that most of her powers require her to have the ability to move, stasis or bodily manipulation would also work wonders here. On character I think would go well here is,

Ashley:

The Great Ashley from WarioWare. Ashley was able to fly her broom all the way to the moon in just over a second and tank the kinetic energy of landing onto it, which should put her nearly on par with this tier in terms of stats, being slightly faster and weaker. Ashley is a very powerful witch who can use a lot of useful abilities against this tier, possessing hax like transmutation, which should allow her to take out the majority of characters in only one shot, disregarding their healing factors. Ashley has far superior movement options than the characters in this tier having flight, telekinesis, teleportation, dimensional travel and even immersion which would easily grant her a tremendous advantage in range that would allow her to snipe any of her opponents with her distance attacks while being able to counter their own. Ashley’s immersion allows her to travel into fictional media such as books or games and take others there, which could be used to effectively seal away any of the characters other than Daisy or Shishiga who don’t stand much of a chance against her anyway. Ashley is also Far more competent and experienced than most of the characters at this tier, having fought demons and other monster like characters innumerable times. Ashley’s by FAR biggest threat in this tier is Mandy, who despite being vulnerable to this same sealing certainly would have a fair deal of counterplay to Ashley, but something else that Ashley can use is Voodoo, which would heavily restrict Mandy’s movements preventing her from using much of her own abilities and even kill her, ntm it can work from other dimensions so the wise Ashley could simply get herself to safety before activating it. Even if Mandy went all in and tried to freeze Ashley in time or Control her mind right out the get go, Ashley could still potentially counter it with The Dark Zone which absolutely messes with an opponent by pelting them with random status effects, including messing with Time and Causing Confusion to throw off Mandy’s powers directly, not to mention do things like warp her underground, shrink her, make her own healing factor do damage to her and all sorts of other stuff that would enable Ashley to win a hax quickdraw with the demon girl. Other than that Ashley also has things like Purification, which I have to imagine would be really rough for Mandy to be exposed to, overall she would be a really difficult opponent for Mandy to beat. That said, Mandy could well take Ashley down if she was allotted some prep time, for a character who would be more consistent.

Mentor:

Mentor from Freedom Force should hypothetically be able to fight this tier as well. Mentor scales to the Greek God, Pan, who moved around his own floating island and his reaction speeds scale to the Domain's spaceships which travel at FTL speeds, more than allowing him to compete here in terms of power. Mentor is an incredibly powerful psychic alien hero, meant to pay homage to both Martian Manhunter and Professor X, so you can bet his mental manipulation powers are really good, more than likely superior to that of the Nazi Telepath Blitzkrieg, and could easily dominate the mind of almost anyone in this tier with his psychic powers. Now there is obviously a big asterisk next to anyone as Obviously Mandy’s Mind Control and Mind Control resistance have better feats than his own and should beat him out, however the real strength of Mentor’s mind powers isn’t its potency, but it’s versatility. For example, his Mind powers make him outright immune to Magic, nullifying the abilities of any of the sorcerers here. They allow him to manipulate time, including allowing time travel, or mind screw someone retroactively in the past, allowing him to likely avoid the time stop, as he was even able to create a Mental Seal that TimeMaster, the multiversal time manipulating deity, could not escape. Mentor can also read minds to see basically any kind of attack coming and use countermeasures to stop it before it happens, or throw people off his trail by causing them to experience delusions. Mentor can also create psychic barriers and use telekinesis which could allow him to prevent his foes from moving, which would stop them from using their metafictional powers. Another amazing power that Mentor has is his ability to move and exist on the Mental Plane such as when he entered Alchemiss’ Dream. Even Mandy cannot defend against someone entering into her mind, when Billy did so Mandy was unaware of his presence and while in there he managed to temporarily disable all of her powers, and Mentor would easily be able to do the same. Even Mandy’s ability to end the multiverse with her Smile may not be good enough to stop Mentor as he was able to hold himself in existence even when Entropy was erasing the multiverse. All that said, It is Possible Mandy with great difficulty could still affect him with her own mental powers, making this not 100% safe for him. For the safest possible option….

The Ghost Writer:

Someone I feel would absolutely be OP in this tier is none other than The Ghost Writer from Danny Phantom. The Ghost Writer is a powerful Ghost easily comparable to Ghosts that can create entire islands with their power, and he could keep up with Season 2 Danny who could outspeed Technis’ satellite lasers which could travel from orbit to surface in under a second, putting him well in the stat range. Naturally, The Ghost Writer is a Ghost and possesses the standard ghost abilities of the verse, including things like Intangibility, which would protect him from a majority of physical attacks, as well as the ability to Overshadow someone, which is possession, something the verse’s characters are specifically vulnerable to. But that’s nothing compared to his main ability, which is essentially the ability to trap people in the poems that he writes using his magic keyboard. What this does is give The Ghost Writer full control over the reality he is effecting, to a frankly unbelievable degree, and would be a similar effect to Grim’s Fairy Tales book which trapped both Billy and Mandy inside and left them no means of exit. The Ghost Writers manipulation over reality in this state allows him to bodily and even straight up mind control the entire involved cast of characters to fulfill his story needs, and it can affect an insane range, not only to actually take possession over the Moon, but he was able to control the Danny Phantom Earth with this while he was in The Ghost Zone, and extra dimensional flipside reality. This Range suggests his control of minds may even be superior to that of Mandy, as crazy as that may seem. On top of that The Ghost Writer can also summon a large variety of different ghost like monsters to fight these characters with until they eventually go down, and really conveniently, seems to gain immense knowledge of whoever he's writing about as seen when he trapped Danny in his story, after just meeting him and not even knowing his name, and suddenly knowing his secret identity and all of his personal relationships and stuff, meaning he would also immediately know every single potential threat this tier could throw at him and plan accordingly. With Mandy’s body being controlled she obviously couldn’t go after him, and since he tends to operate from another plane of existence, he’d be out of range from any retaliation she could do without moving like her time manipulation or mind control, basically meaning they are all screwed to live out his Nightmare Before Christmas.

Star Tier:

This is the tier of big name threats of the Underworld and Beyond, it includes numerous of the most powerful and iconic monsters in the series and is also the Tier that Grim would occupy without access to his Scythe. Top tier underworld monsters can rearrange the planets like nothing and are stated to be capable of Destroying Stars, something which was directly proven when Nergal broke the Sun simply by accidentally hitting a baseball too hard. Speed wise, merely hitting a baseball all the way to the sun in under a second would already mean Nergal swung his arms over 500 times the speed of light, Mistress Pollywinkle on the other hand, was able to blitz Grim while he had his Scythe, which would require speeds of at least 90 Billion times the speed of light. One of the most well known monsters at this tier is Nergal, a dark demon from the center of the Earth. Nergal can produce tentacles and giant limbs from his back, which can stretch longer than the Radius of Earth and produce powerful electric shocks on contact. Nergal can fire massive blasts of energy, telekinetically pull an entire Circus through the Earth’s crust and most terrifyingly, use his tentacles to Transmutate others into Nerglings and mind control them to be his friends, this attack is so potent it can hit and effect Mandy, Grim and even hit the absolute plane and hit the shows viewer. Nergal’s half-human son Junior on the other hand is even more dangerous, having all his father’s powers and more. Junior can shapeshift his form and voice into anyone or anything, and can use this power to do things like turn his body into liquid, dramatically increase his stats by changing his muscle mass, fly through the air, turn parts of his body into weapons or consuming mouths, and even spawn henchmen from his biomass and break them off his body. On top of that, Junior’s true form is so horrible and terrifying that it can make people's heads Melt on sight. Junior can also turn completely intangible, shoot webs to restrain targets, and place people into a state of stasis where they cannot move or think. One of the most widely broken things in this tier is the large number of movement options the Characters have, being able to do things like teleport, travel to other dimensions and even overlap themselves with reality, like Lord Pain, who can hit and shatter the metafictional 4th wall. Pain can also drastically increase his size, speak in a forbidden language that deals spiritual damage to all mortals that hear it. Killing plants and animals and causing sickness and madness and phase matter into and out of existence. Several more characters such as the Tooth Fairy can transmutate foes, and the serpent teacher Ms. Slither is able to summon basically any type of matter she wants to her side, including both objects and sentient life. Other common powers here include Super Senses, Fire Manipulation, telekinesis, and energy manipulation. There's an army of alien Werewolves as well as the Martian Grim Reaper, who both independently have the ability to turn the entire human Population into Zombies, ntm you have intelligent characters such as The Creeper who can invent Time Travel. To get into some more Big name characters, The Boogeyman, one of Grim’s arch enemies can shapeshift into anything, possess objects or immersion himself into things, but by far his best power is his Nightmare Hypnosis Trap, where he puts someone to sleep and traps them in a series of infinite horrible Nightmares that just get worse and worse as they go until the victims will is completely broken and they serve him, not even Mandy could counter this. The Spiderqueen is a giant extra dimensional spider who can turn people into spiders, control all spiders with her singing, can trap the world in a giant web, use potent venom and has Knowledge of the fourth wall. There's also Headmistress Pollywinkle, an extremely powerful Dark Witch who has the ability to suck people’s souls out of their body and gain their skills. Even worse than this is Fromabular, a magical reality warping skull, who can do all sorts of things like levitate, manipulate time, create beings from scratch, make star sized explosions, change people's gender, answer any question, and generally change reality like a genie. However there IS one more character to talk about that many people may be surprised to see here, and that is none other than Irwin! Yeah despite being a wimpy and lame nerd for the entirety of the show, Irwin in reality is Half Mummy and Half Vampire, and thus has the powers of both and easily makes this tier. Irwin can regenerate from immense injuries like being broken to pieces or being turned to dust, use a power known as Mummy's Curse which lets him control insects and snakes and fire magical blasts, summon armies of Scarabes that turn everyone they touch into undead Mummy Minions, resist age manipulation with immortality, fly, manipulation his wrappings like snares, turn into a bat and open dimensional portals. 

So what strategies would allow someone to stop this tier? This tier has a lot of potent antagonist Characters who are meant to be taken quite seriously, and thus are much more competent and smart than the average from the previous tier, and their dimensional travel powers are actually really strong so the same strats from the last tier won’t work that well, so what will? Well this tier has a lot of powerhouses and potent offensive hax, having oneshot powers, the ability to create armies at will and decent versatility, but they don’t actually have a lot of defensive abilities other than some potent regen, many of their own powers have shown to be just as effective on them. The hax resistances in this tier simply are not as good as they are in the previous tier overall, meaning if you can find a tank like character who can defend against all of their stuff, with just a couple potent hax attacks, they could potentially outlast and defeat them. One character I think could do this,

Arakune:

The terrifying blob creature, Arakune from the Blazblue series. Since he's from the Blazblue series one should probably gather that he does in fact scale to around the level of Makoto, who can super casually destroy the moon at faster than light speed. While Arakune is unlikely to overpower the verse in raw stats, there's a lot more to it than that. Arakune’s body is composed entirely of Seither, the energy substance of Blazblue that has existed in all space on Earth since the death of the Black Beast. This grants him Logia abilities including shapeshifting into basically anything and regenerating from being splattered into small pieces, so those stats won’t have too much luck putting him down anyway. Seither also causes those near it to become poisoned, driven mad or have their powers drained away from them, which are all things that characters in this tier don’t have any particular defense against. Speaking of defenses, Arakune has a lot of those, including potent resistances to Transmutation, Mind Manipulation, Stasis and Spacetime Manipulation, nullifying the powers of The Tooth Fairy, both Nergal's and Lord Pain all at once. In addition to that Arakune’s soul is sealed within The Boundary, and thus isn’t available for Headmistress Pollywinkle to attempt to steal. Ararkune has massive super sense that would enable him to track down anyone in this tier through their levels of Dark Power, where he would try to absorb them. When Arakune absorbs someone, it consumes their soul, gives him all their memories and powers, and seals their body in The Boundary, meaning its extremely unlikely anyone in this tier would be able to survive that, and Arakune is only going to grow in danger the more he does this until eventually winning. Arakune also has power over Insects, which could allow him to hijack the armies of The Spider Queen, or turn the insects from Irwin’s Mummy Curses against the verse where they could turn everyone into zombies. Arakune can also do lots of recon by turning invisible or using his clairvoyance to spy on his targets if wanted to, and the fact that his attacks can nullify crazy high Regen only speed up the process of his victory. All that said, Arakune is extremely insane and potentially could be stopped by Boogey's Nightmare Hypnosis spell. Unlikely to happen, but if you are worried about that spell,

Charmcaster:

You can always use Charmcaster from the Ben 10 franchise. Charmcaster was able to overpower Anodite Gwen, who could wipe out the Highbreed warfleet which tanks the Dwarf Star levels of energy coming off of violently shattering planets, she can also keep up with Chromastone, who was able to fly halfway across the galaxy in only a short time, putting Charmcaster perfectly on par with this tier in terms of stats. Abilities wise, this is a whole different story! Charmcaster’s main ability is her connection to Ledgerdomain, the dimension that is the source of all magic power in the entire Ben 10 Multiverse. The only way to enter or exit Ledgerdomain is to know its True Name, which due to a spell that Charmcaster controls, changes every few seconds, making it virtually impossible for anyone in this tier to enter into her dimension, or escape from it once there without Charmcaster herself allowing it. This means that Charmcaster has the option to simply fight everyone in their tier in a series of one on one fights if she wants rather than everyone at once, and with her large arsenal it's unlikely anyone could defeat her in a 1v1. Charmcaster has vast super senses that allow her to spy on foes on Earth from her own dimension meaning she could also study and make strategies for how to deal with her foes before having to fight them. On top of that, the vast majority of threats contained within this tier simply will not work on Charmcaster due to the fact that ledgerdomain is her Territory, and magic cast from other sorcerers is unable to affect a sorcerer in their own territory. This would allow Charmcaster to shrug off even extremely potent spells like Boogey’s Nightmare Hypnosis, The Tooth Fairy’s Transmutation, Headmistress Pollywinkle’s Soul Steal, and Irwin’s various Curses, which are all expressly magic. Even against the other various characters, Charmcaster has a lot of potent spells including telekinesis, illusions, simulation summoning, animacy granting, various magical blasts and elemental manipulation to keep them on the back foot, and one of her greatest powers, Energy Draining, allows her to drain the lifeforce out of an entire dimension at once, up to even universal scale, as well as resist someone using similarly potent energy draining ON her, something that could one shot anything here from a great distance. Charmcaster’s greatest threat here is likely Junior and his Father using their tentacles to Mind Control/Transmutate her into one of the Nerglings, but Charmcaster ALSO has Mind Control and Transmutation which do not require physical contact to pull off, meaning she's far more likely to land this kind of attack on them. All that said, Charmcaster IS kinda insane, and if she had a major lapse in judgment it’s possible for one of this tiers characters to take her out, for the safest possible option.

Courage:

You simply cannot get much better than Cartoon Network's premier Monster Counter, Courage the Cowardly Dog from the series of the same name. Courage is powerful enough to shatter entire stars just by screaming, could keep up with The Shadow who could fly to other Star Systems in under a second, and pilot space ships that were even faster than that, meaning Courage should be able to compete here in stats pretty easily. Courage is extremely weary of all threats due to living in a place where absolutely terrifying monsters run rampant, and treats every creature extremely seriously, and he is superhumanly competent at stopping them through intelligence and various skills he has developed on the fly, including things as advanced as learning how to fly a plane, become a licensed therapist and master buddhist magic in a very short timeframe. This tier REALLY Doesn’t have anything that Courage hasn’t personally seen before, having dealt with King Ramses who has similar curses to Irwin, Stopped advanced Dream Manipulators and Soul Stealers, and was able to purge Muriel of a demon possessing her. Courage has a wide variety of Hax resistance, including the ability to reverse his own Transmutation with his shapeshifting powers, and use the power of Love to Shrug off Mind Control, including ones from the literal Gods of the series, meaning that even Nergel’s Nergling transformation power likely would NOT WORK on Courage. Courage also has his own hypnotism which likely could affect anyone in this tier, as well as the ability to Seal foes in fictional media with Immersion, which only Lord Pain and Boogey have the ability to come back from. And in terms of physical fights, not only is Courage a Master Martial Artist who was able to fight ancient chinese super warriors, but his Regeneration can allow him to come back from ashes which is superior to any Regen this tier’s characters possess and primes him to win a war of attrition. But if all that wasn’t enough, the fact is Courage is a small and cute pink dog, not only would the characters at this tier Not consider him any kind of serious threat, but they actually all LOVE Dogs and think they are adorable, which would more than give Courage the chance to pull whatever he wanted first.

Universal Tier:

The strongest tier in Billy & Mandy is a tier of Gods, Legends and Death itself, cosmic horror threats beyond mortal understanding that are always treated as a huge deal. Characters in this tier are repeatedly stated to be capable of wiping out the entire universe and ending time as we know it, and can easily travel intergalactic distances in no time flat, putting them at Universal+ and Billions of times the speed of light just in their base states. That being said, these characters also have the ability to bolster their own stats, such as the time Grim pumped Mandy full of so much power, she expanded infinitely at an infinite rate until she would eventually outgrow the multiverse, meaning any of these characters could raise their stats to Infinity if they so choose. A pretty obvious character to start with is Grim, who wields Jody an incredibly powerful Scythe with the cursed power that leaves any injury caused by its blade permanent, nullifying any ability that would otherwise fix the damage. This Scythe is one of the most powerful and versatile weapons in ALL of CN, able to casually warp reality and all of space and time on a Universal Scale. With this Grim can create dimensional portals to any plane of existence in the multiverse, travel through time and even persist after the end of time itself, teleport, fly, stop time, spatially sever objects, and even see and move through metafictional space. Grim can also regenerate from ashes, possess people, create matter, use telekinesis, shoot lasers, fuse things together, transmute matter, see the future, raise armies of the undead, animate objects, control minds at a high enough level to effect Mandy, shrug off Soul Hax and Existence Erasure, and manipulate Death, Fear, Magnetism, Memories, every single Element and much more. Beyond him this verse contains numerous Gods including the Greek Goddess of Chaos, Eris. Eris is the Platonic Concept of Chaos, and is passively responsible for all Chaos in the multiverse with merely her presence, not only does this mean her Chaos Manipulation is incredible and she can regen from her concept, but should she be destroyed than so would Chaos, which is really bad because without Chaos, Order cannot exist, and without Chaos or Order, nothing would exist at all. Eris can also use basically all the same powers Grim can, and has additional things like Clairvoyance, Duplication and the ability to send foes to The Puppet Dimension, which metafictionality changes the Animation style to Puppetshow so they lose all their powers. There is also Father Time, the God of Time who is Time itself. He has Complete control over time, able to manipulate time, including things like his foes aging, and can add or subtract time to cause or reverse people's deaths. He can even erase people permanently from time and memory completely. But Billy & Mandy doesn’t just have the Greek Pantheon running around on this tier, it also has the Lovecraftian Pantheon, and unlike Invader Zim, it is actually Very Reverent of them. Yog-Sothoth is an extremely powerful extra dimensional entity who can open portals that can only be sealed by his own power. He can possess any mortal through mere mentions or viewings of his work and raise their stats high enough to beat Grim, plus he can warp reality itself in the dimension he enters, corrupting it into his plane. There is also Cthulhu, a monster beyond space and time, which can drive anyone that gazes at him completely insane, pull anyone through intra-dimensional portals (except for their shoes), spawn miniature versions of himself, and can transform anyone that hears his voice into monsters and squid creatures. This verse also has a few gods of its own, such as Pinface, a Netherworld Entity that can only really be defeated by the solving of his puzzle box. He is outright immune to the supernatural energies of the scythe and has powers like banishing people to an eternity in the netherworld which even grim could not escape, as well as fire manipulation and control of vast armies. Horror, The Ancient, God of the Underworld was able to use Fear Manipulation to create Horror’s Hand, the most powerful Fear Manipulating Device in the entire series, able to terrify someone to such an insane degree they can literally Explode. But beyond all that, is none other than Future Mandy, Yes, Yes she's Back! You see in the Future of Billy & Mandy, Mandy turns herself into a powerful Wormlike creature who has all Mandy’s same powers, and was able to conquer all of reality due to being Immune to EVERYTHING in the series, so, that’s a thing. So how does one reasonably fight this verse? Well what if I told you that basically everyone in this tier shared one pretty glaring common weakness, and that is the fact that every single one of them relies at least somewhat on tools to pull off their abilities. Grim’s scythe is the source of the vast majority of his powers, Yog needs his Book, Cthulhu needs his Phone, Pinface needs his Puzzle, Horror needs his Hand, Father Time needs his Hourglass, seriously it's actually pretty comical how they balanced it so weaker characters could potentially score a win against them by stealing their stuff. Even the characters who do not rely on objects for their power, namely Eris, still have The Golden Apple of Discord, which can give someone who takes it a similar level of Chaos Manipulation to fight her with. Beyond that I believe that since this tier has a lot of reality warping and 4th Wall Manipulation abilities, having characters that can also do that as a way to match would be optimal, one example of what I’m talking about would be, 

Bobobo-Bo Bo-Bobo:

Anime’s Greatest Hero, Bobob from the infamous Bobobo-Bo Bo-Bobo series! Bobobo is capable of creating and maintaining an entire universe with his own power, and flying to other galaxies in seconds, which means he's on par with the characters in this tier’s base stats. While these characters can rise above him in terms of stats, Bobobo has a Low Godly healing factor, which allowed him to regenerate after being turned into a skeleton….but in a completely different location meaning he did come back from nothing even though his skeleton was still there. Bobobo has immense Reality Warping abilities that work on the 4th wall, which technically gives him the means to affect whoever he wants in this tier. He’s got crazy powers that blatantly do not make sense including the ability to somehow hurt people by doing mundane tasks, and also use powers like Transmutation, Duplication and the Dreaded Bobobo world, where he generates his own dimension around his foes which drives anyone inside completely insane, which is something only really Eris can endure unscaved. Bobobo also has an alt version of this power called Bobobo Nightmare World which destroys anyone Evil that is trapped inside, which would be devastating against the Lovecraftian Gods and Pinface. He also has a crapton of random resistances that protect him from Transmutation, Mind Manipulation, Existence Erasure and use the “Hickey of Bobobo” to nullify a foes powers entirely. Bobobo’s best power is called Ganeme, the ability to assert his reality over another, rewriting the show however he wants. Bobobo’s Ganeme is so potent that it straight up gives him Math Manipulation, allowing him to make 3+3=8 and have it be correct. Math Manipulation gives the user abstract control over all reality beyond even normal concepts and could potentially be used to rewrite even Eris’ existence being tied to the universe, giving Bobobo the ability to defeat her. Of course, Bobobo is also a completely Insane person who is not the best at tactical thinking, meaning the potential for someone to take him way more seriously and find some way to stop him with their own power is totally there. For someone a bit more competent than him,

Zatanna:

Another character I think would be able to do exceptionally well is none other than the Great Zatanna Zatara from DC Comics. Despite not being anything special for this tier in terms of physical stats, just like the Billy & Mandy Gods, Zatanna’s magic can raise her power level to be absolutely mind bendingly strong and fast, to the point of casually effecting and traversing the multiverse and beating back monstrous entities like Pralaya, and she should casually be able to do the same here. Zatanna’s Magic is not only extremely powerful, but precise, being able to do basically anything the characters in this verse can, including traveling through and stopping time, controlling minds, traveling across dimensions, erasing foes from existence and stealing peoples powers. Doing something as simple as detecting the source of these characters' abilities and separating them from it would not exactly be that difficult for her. Zee is a much more competent and serious fighter than basically anyone in this tier, which would result in her taking them more seriously and likely winning any quickdraw with them as a result. Zatanna’s magic is actually so advanced it, just like the characters within this tier, is able to manipulate the Metafictional plane to some extent, as shown in her epic battle with Zor, where she began pulling the very comic panels down on top of him to best the dude, which means Zatana could potentially block attacks that are attempting to hit her on this plane as well. Her magic is described to work as asserting her own reality over that of the reality that currently exists, allowing her to alter the fabric of reality in a similar manner to the concept of Hermeticism, with this she could potentially rewrite the defenses of Eris, Father Time and even Pinface who could outright resist Grim’s Magic. With all that said, Zatanna is not naturally immune to all the various threats in this tier, and would have to keep on her toes at all times when fighting these characters or she could wind up getting haxed herself. While Zatanna is VERY used to fighting under those conditions, if that risk is still to great, then,

Kasen Ibaraki:

Yeah if you want a way to literally Break the Order-Chaos Balance of Billy & Mandy, look no further than Gensokyos Oni Sage of Nature, Kasen Ibaraki from Touhou Project. In her Oni Sage form, Kasen is literally the Strongest and Fastest character in the Entire Series, being so powerful that Gensokyo cannot handle her, and even the Infinite Hell will eventually implode from her passive presence, meaning she could easily compete with ANYONE here in stats. Kasen has a great deal of magical powers that would be considered broken in this tier, including her ability to manipulate shadow limbs such as her own false arm, which can phase into and out of reality in any location and take things with it, allowing her to effectively snatch objects from users no matter how securely they try and hold onto them. With that alone Kasen can easily depower the vast majority of characters here by taking their source of power, and she would easily be able to tell these are the source of their power due to her adherent ability to read an item's supernatural energy. As befitting a Sage, Kasen has an insane deal of powers and resistances that would allow her to counteract most of the things in this tier the characters tried on her, including Acausality, or the ability to exist outside of time, which shuts down any time related powers. She was also able to shrug off the advanced Mind Manipulation powers of Satori, soul manipulation from various ghosts, and should be able to Manipulate Space to a similar degree as fellow Hermit, Miko, and likely would be able to seal away anyone in this tier as a result. Kasen can literally destroy someone’s spirit and completely erase them from the cycle of death and rebirth to counteract any form of regeneration. Speaking of Which Kasen is SO Strong as an Oni that she was able to Render even Reimu’s Metafictional Sealing ability, Fantasy Seal, useless against her, which suggests that not even the Metafictional attacks in this tier like Eris’ Puppet Dimension would be able to stop her. Even when Kasen allowed herself to be defeated and had her entire body destroyed, she just regenerated back from nothing. But what about Eris? Since Eris is the Goddess of Chaos, Kasen cannot kill her without ending existence. Well Kasen is pretty used to dealing with the Chaos Sage, Yukari and unlike her, Eris doesn’t actually have defense against conceptual manipulation, something that Kasen has and could simply use to alter Eris’ Nature so that Chaos no longer depends on her, thus meaning Kasen CAN in fact permanently beat her without harming the universe. Beyond all of that, Kasen is the Nature Sage and has power over all animal life, since the Lovecraftian Gods in Billy and Mandy are similar to Beastial Yokai, it’s likely Kasen could simply control them and use them against the verse as her own army and, yeah they really aren’t going to be able to defend against that. Better yet, since Future Mandy turned herself into a WORM to gain her power, this Beastial Control ability would apply to her as well, as the level of intellect that the animal has does NOT matter.