Uni-power has its limits. It's only supposed to amp a person x50. I remember when DD had it for a while, and he was hardly cosmic level. Spider-Man is a notable exception, but Surfer once pwned a guy who had beaten Gladiator without the uni-power, then he became cpt. universe and Surfer still beat him.
I'd say Thor, honestly, but it probably depends on who's writing the uni-power.