I would personally say it's Brainiac. Sure, Doomsday may have killed him, but Brainiac killed the finest man Clark knew - his Pa.

Lex, easily.

Lex Luthor. There's no contest.

1.) It's Lex.

2.) Brainiac only killed Pa in the post-Crisis - pre-52 era. Pa dies of natural causes in the Golden Age, pre-crisis and Vyn kills them in the N52.

Lex Luthor is his archenemy

What they say ^^

Superman - Lex

Batman - Joker

WW - Cheetah, though a case could be made for Ares

GL - Sinestro

Flash - Grood

Aquaman - Black Manta

Lex is his archenemy, because their personal values clash naturally, and also because Superman incarnates everything that Lex hates. The mere existence of Superman hinders Lex's world view.

Brainiac is his enemy because he wants to harm people and Superman won't let him, and they have massive clashes in their histories, but it's not that personal and it's not that fundamental.

Lex

@superguy1591: for flash it is reverse flash

Luthor.

Its Lex, no question. Brainiac comes in second but it really isn't close.

Ok. Has Lex ever done anything to Superman's loved ones though?

@superguy1591: I agree, except for the Flash. Reverse-Flash would be the more likely candidate.

Actually for flash it's Professor Zoom

And War is no longer her enemy in the New 52m he is actually trained her as a kid & now she is the new god of war.

This.

He had Lana tortured in Byrne's run. And I get the feeling he's always sexually menacing to Lois.

Lex

@superguy1591: grodd? Come on lol the flashes arch nemisis is captain cold

Far and away Lex Luthor.

I can understand why you'd think Brainiac was Clarks true archenemy and it could be argued he has multiple but I think just based off of mass media, Lex is deemed his archenemy. People, casual and common, know Superman vs Lex and may not know Superman vs Brainiac or Superman vs Doomsday or Superman vs Mr. Mxyzptlk.