He is currently working with a secret government project that intends to kill Superman.

He is one of the many villains trying to kill Superman.

The enemy that accomplished the most, by actually killing Superman, is the raging monster Doomsday.

He is best known as the character who killed Superman.

Doomsday is the only being that has ever managed to kill Superman.

Or, he could kill Superman directly with the Killing Curse.

He even went so far as to send a nuclear warhead just to kill Superman, willing to kill innocent people to do it.

The gathered heroes try to kill Superman and Batman.

He was sent to earth to kill Superman.

She is defeated in a few seconds after she tries to kill Superman by stepping on him.