Darkseid, and as much as I am not a fan of this guy, H'el.
Then Doomsday & then Zod. Braniac is not that menacing, I mean come on he beat him before his first year as superman ended.

@deaditegonzo: Well aside from Mxy, I agree lol

Mr Mxy, Prime, Darkseid, Zod and brainiac

Jesse Eisenburg

Has anyone mentioned Riot? He can't die and the more superman hits him, the stronger he gets.

TOAA,Beyonder,The heart of universe,LT

I'm joke

I'm almost positive that Mr. Mxy is the most powerful, which is why the character isn't "evil." He just likes to have fun at other people's expense.

Lots. Doomsday,Darkseid,Black Adam,Lex Luthor,Brainiac,Zod,Mr Mxy

Mongul (Pre-Crisis)

Darkseid (Pre-Crisis and True Form)

Imperiex Prime

Doomsday (Hunter Prey)

General Zod