I'm gonna go with Namor. Bad enough he's a crap king/eco-terrorist of a collage frat-boy and everything, but the dud leader teamed up with Thanos of all people to destroy alt. universes. A galaxian class psychopath who culls other psychos to his cause of murder and genocide for cruel fits and giggles for a hobby no less. Even Namor flinked out on how massively he f'd up after the way he saw his Cabal brutalize every new universe they came across. And for no real reason other than the evuls, they literally took their time butchering realities when all they had to do was initiate Antimatter bombs and be done with it.