Lex Luthor

Lex Luthor is Superman's arch-nemesis. He's the leader and usually the brains of the Legion of Doom. Lex Luthor occasionally sports a power suit that makes him much more of a physical threat to the Justice League of America.

History
Luthor was originally from Smallville. He was good friends with Superboy, until a lab incident caused him to be bald, thanks to Superboy. This of course was an accident, but nevertheless, Luthor held a grudge against Superboy, and vowed that one day he would kill him.