Ultraman - the scariest villain in Superman Series

 Ultraman is a dark, twisted version of Superman from an alternate universe (Earth-3 in DC Comics). Unlike Superman, who fights for truth and justice, Ultraman is a ruthless, power-hungry tyrant and a key member of the Crime Syndicate, an evil counterpart to the Justice League. Instead of being weakened by Kryptonite, he's empowered by it, and he comes from a reality where good and evil are reversed. As one of the scariest Superman villains, Ultraman represents what Superman could become if his power was corrupted.