Sublime and Kick, aka the U-Men, make the most of their limited screen time to stand out as truly horrifying monsters. A pair of mutant-hating murderers, the U-Men are known for kidnapping mutants, specifically young teens, then sadistically butchering and vivisecting them, using their organs to upgrade their own cyborg army. Along with this, the U-Men test out an experimental serum on innocent mutants that transform them into abominations in constant pain. When Kick fails at killing the X-Men, he wantonly opens fire on them along with the numerous teenagers and police officers in the area, trying to kill anyone he can. Sublime, having left Kick to his fate, returns with a powerful suit of armor and before blowing himself up in one last attempt on their lives. Both spend their last moments proclaiming their hatred and disgust for all mutantkind.
Mastermind, real name Jason Wyngarde, is the leader of the Inner Circle, a group of mutant supremacists, and the one responsible for Jean Grey's rampage across a city and her death by transforming her into the Phoenix, framing his former lover, Emma Frost, as revenge for Frost leaving him. Working with the mutant-killing U-Men, he fully endorses their crimes, using them to learn of a powerful mutant residing in Japan, where he uses his abilities to ingratiate himself into the lab staff of mutant researcher Yui Sasaki. Learning that the powerful mutant is Sasaki's teenage son, Takeo, who has reality-warping powers, Mastermind spends months secretly using his powers to psychically torture the boy, eventually into a horrifying state of death-longing insanity. While holding numerous X-Men hostage, and using his powers to torture Cyclops, Mastermind reveals he plans to unleash Takeo's powers on the world like he attempted with Jean Grey, then watch the worldwide destruction and chaos that unfolds before him. Believing himself and all mutants to be the Master Race of the Earth, Mastermind treats his atrocities as his "right" for being at the top of the evolutionary food chain.
Ho Yay: Between Cyclops and Wolverine. You'd have to be blind not to at least once think "will they just get a room already?"
Moral Event Horizon: When the U-Men try targeting kids just to improve their power, you know they've gone too far.
which sounds truly epic.