Ultimate X-Men/YMMV


 * Ass Pull: Pyro introduced as one of the good guys and made into a villain in Ultimatum
 * Complete Monster: Magneto, in a marked change from his usual Noble Demon status. Sometimes he makes Grant Morrison's Magneto look shy. For a start, though Retcon gave him his more familiar background, originally Ultimate Magneto came from a wealthy American family and was never on the receiving end of a genocide or any sort of prejudice, meaning initially he didn't even a Freudian Excuse for his actions and was even more of an arrogant dick . No Well-Intentioned Extremist Anti-Villain as the mainstream one is, this Magneto is an abusive parent who once broke his own son's legs for challenging him; is a true mutant supremacist who believes that mutants should replace humanity rather than merely be protected from them (in fact, he's even implied to have been eating humans at different points); and has, on several occasions, attempted to eradicate the human race and rule over a post-apocalyptic mutant utopia in the aftermath as an extension of this creed. He is savagely ruthless to his enemies and, here, is the one who crippled Charles Xavier, because the latter had started to realize he was insane. He rules the Brotherhood of Mutants like a cult and encourages them to murder as many humans as possible, children included, and has organized several terrorist attacks with high body counts. Death is too good for this prick.
 * Colonel John Wraith, head of Weapon X, was set up as a brutal, remorselessly sadistic bastard who tortured all the mutants in his "care" for shits and giggles, particularly Wolverine, Rogue, and Nightcrawler (At one point he tells Rogue that whether he breaks her arms and legs again depends on how bored he is). He eventually ended up being shot by Nick Fury. And then at the end of the series they brought him back as Ultimate Vindicator to redeem himself, which completely flew in the face of his previous characterisation.
 * Ultimate Deadpool and Ultimate Mojo run a television show where they hunt down mutants for sport and whose plan includes trying to murder the X-Men while forcing Xavier to watch and then lobotomize him on live tv. Mojo was Mind Raped by Xavier and killed, while Deadpool appears to have survived Shadowcat destroying his body.
 * Ensemble Darkhorse: Pyro had very little screen time, only a few lines and didn't do much, but the fandom loved him.
 * Ham and Cheese: The adventure scenarios Nightcrawler and Colossus play in the Danger Room, everything from Pirates of the Caribbean to The Lord of the Rings.
 * I Am Not Shazam: Dazzler was originally the name of Allison's band, which she insisted on reminding people, but eventually became her codename.
 * Moral Event Horizon:
 * How about everything Magneto does, to unflinchingly attempting genocide of the human race, to kneecapping his own son? And the Weapon X crew, particularly Wraith? Wraith and Magneto don't cross the Moral Event Horizon, they are living, breathing Moral Event Horizons.
 * YMMV on this, but Mr. Sinister pushing Professor Xavier down a flight of stairs. That's just cruel, not to mention extremely petty.
 * It also qualifies as a Crossing the Line Twice moment.
 * For some, Wolverine crossed this when  That bites him bad in the ass when  ...