I agree with Logan, on Krypton, Ali takes out the Last Son. On Earth, Kal-El wins with a flick of his little finger.
I must disagree with Logan that Ali wins against anyone on a level playing field. If we're going super heroes, Wolverine (with or without powers and claws), Captain America, or Batman all crush Ali quick.
In real life, with no holds barred and adjusted to each fighters prime age for fighting, I think a ton of people could take Ali. Bruce Lee, Ken Shamrock, and of course, former Orioles manager, Earl Weaver.
In a straight boxing match, Ali beats everyone, including a young Mike Tyson.