29. Sinister

Like Apocalypse, who made him into the super powered menace he is, Mr. Sinister is obsessed with the Darwinian idea of survival of the fittest - but this genetic manipulator goes to some extremely dark and cruel places to further his beliefs and experiments, sometimes outdoing Apocalypse himself when it comes to truly evil acts.

Once upon a time he was a 19th century scientist named Nathaniel Essex, who had no quibbles experimenting on the homeless and those he saw as societies (and humanities) refuse. Transformed by Apocalypse and now known as Sinister, he's now lived decades past what should have been the end of his life, continuing to manipulate and destroy mutants and humans as he sees fit.

While he wouldn't physically appear for another year, the first time his name was mentioned was during one of the darkest times in X-Men history - the Mutant Massacre, in which he sent his team, the Marauders, on a merciless mission to kill the Morlocks, which also resulted in severe injuries for Kitty Pryde, Colossus, Nightcrawler and Angel. Later, we'd learn of Sinister's obsession with Scott Summers and the Summers genetic line, which led to him creating a clone of Jean Grey - Madelyne Pryor - with the sole purpose of breeding with Scott. The result of that successful quest led to the birth of Nathan Summers, AKA Cable.

Having survived seeming death multiple times, Sinister has most recently been reborn in a female body, Miss Sinister. But regardless of his/her exact name or genetic makeup, this is a twisted individual you don't want to turn your back on.