Today, if you had to bet your entire bankroll on one fighter. Every guy in MMA, in a tournament. All fights are 1 round, unlimited time, no breaks, until one guy quits or dies. March Madness style. No need to get to technical. You can take a big guy because he has the size and power. Or a smaller guy b/c he has cardio and quickness. If you have to put everything you have on one guy, who is it?
All things considered, toughness, heart, power, strength, skills, stamina.
I would have to say i'd take fedor. I think his combination or skill, power, and mental toughness would overwhelm most opponents, even smaller quicker guys, before they would be able to wear him out.
Another guy who i would like is Don Frye. Not because of his skills. But because of his insane toughness and heart. If his life depends on it, it's hard for me to see Don Frye quitting.