That they did. Heart and durability are extremely important in reaching greatness. You can get away with average durability if your other assets compensate but you have to have heart.
Riddick Bowe, Lennox Lewis and Mike Tyson. Wladimir Klitschko maybe ? Because he manhandled Povetkin rather easily and Povetkin is a lot bigger than Frazier but if the referee didn't have any of that and forced Klitschko to stop his excessive clinching and shoving i think Frazier would wear him down and then brutally KO him at some point