There were photos from that fight that caught the moment Ali landed a straight right and turned George's head around like Linda Blair in the exorcist, spraying sweat so furiously it looked like a grenade had been set off. Ali's ability to land power shots quickened Georges exit.
Even McCall would have gotten stopped if he swung for the fences and emptied his gas tank while getting countered all night. Anyone who finds this ridiculous has never been gassed in a fight. You are weak as hell when that happens and even jabs hurt you.
Incredibly durable. Some of the big punchers of the 90's would rather box than trade shots. Ultimately, the best of the best like Holyfield, Tyson, Bowe, Lewis and possibly Ruddock and Mercer might've posed some problems. As it were, Foreman never touched the canvas during his comeback. Really something.