That's cause Heavy Weight MMA cage fighters are the ultimate killing machines. They're the pinnacle of fighting athleticism. You take the greatest boxer/greco-roman wrestler in the world and put him against Junior Dos Santos and your guy is dead in 2 minutes. So it's pretty much useless to discuss disciplines that don't mean shit when an actual fighting starts where there are no rules like "oooh, you can't kick with your feet... and you can just hug your opponent and rest for 2 minutes if you're into that kind of thing".Your question is oddly specific: firstly not just any athlete, or even fighter (allowing therefore for boxers, Greco-roman wrestlers, single-discipline martial artists, etc.), or even just MMA fighters of any variant expect cage-fighters.
Heavyweight MMA is THE fighting. Everything else is a fucking circus show.
That's cause there's no way in hell a lightweight could beat a heavyweight. He'd be faster, but once he catches that hit (and he will, eventually), he's down. Oh, and he wouldn't be able to inflict any damage at all, even if the heavyweight guy just stood there, trying to solve math problems in his mind, the lightweight guy would only be a small nuisance.Secondly, you leave out the dozen other weights and require specifically heavyweights.
You probably have gathered by now that I'm not a boxing fangirl, so I don't know that fight and it most likely isn't relevant to an actual fighting discussion.I'm going to take up your questions partially by saying: "Ali vs. Foreman."