Doomsday, easily. Doomsday evolves beyond whatever can beat him. Blast him with sonics and doomsday will become immune the next time you face him. Toss him into the vacuum of space. When Doomsday returns, he won't need to breath. You can fly and Doomsday can't? Doomsday's claws will evolve to the point where they can shoot out and retract like Spiderman's webs.
Doomsday is single handedly responsible for the extinction of entire planets--because he killed everything on the planet with his bare hands. He moves at super-speed. His claws cut Superman and have a toxic poison in them. Doomsday is death. Even Wizard magazine did this face off, years ago and said that, "Unlike the other face-offs they've done, they believe that Doomsday would KILL his opponent--the Hulk." Even if Hulk were stronger, Doomsday will grow stronger while they fight. That's Doomsday's power--to overcome. He'll never be beaten the same way twice and Superman already punched him to death. Ask The Radiant from planet Calaton. Oh, you can't. He's dead.
