Is Lex Luthor black?

If this is referring to the Superman movie made in 1978- that would be Otis played by Ned Beatty.

As a teenager, Lex Luthor invented a kryptonite antidote to cure Superboy of kryptonite poisoning, but he had an accident in his lab and caused fumes to escape. Superboy used his super breath to...

Not exactly- he does have some good motives. But he always tries to destroy Superman and that certainly makes him a bad guy to the Man of Steel himself.

Batman hands down

He has not ever died in any of the films that have been made so far.