Sebastian Shaw/Black King of the Hellfire Club
Sebastian Shaw, also known as the Black King of the Hellfire Club, is a supporting antagonist in the Kingdom Hearts Unlimited Saga, first appearing in "Birth of A New Era" as a member of the Separatist Alliance, then reappearing in "0.2 - A Fragmentary Passage" as the big bad of the Cuban Missile Crisis campaign.
A particularly power-hungry mutant with the power to absorb any form of energy to avoid injury and augment his physical parameters, Shaw longs to make himself the rightful ruler of Midgard out of pride of being the strongest mortal being as far as he's concerned, allying himself with the Nazi Schutzstaffel branch of HYDRA and its leader the Red Skull under the guise of his brother to help him root out latent mutants and bring them to their side through experimentation as soldiers in their path of conquest. Later on during the swingin' 60's and the height of the Cold War, Shaw founds the Hellfire Club, a remnant of the Separatist Alliance mostly including mutants with his similar brand of thinking, with the intent of carrying out the will of their ancient god En Sabah Nur by jump-starting World War III, destroying all of mankind, and plunging the world into darkness through which he and his army will rule afterwards.