If you define tough as the ability to both take and give a blow then you have to with the big men. If, on the other hand you are looking at who can take the most punishment then that is another matter. AI takes a beating most games and just keeps coming. But, I think you probably mean the guy who can both take and give the most. Wilt is hard to argue against. I read recently that he bench pressed 465 pounds, an oh yeah, that was at age 60. He even said he could probably do a little more. As far as pure strength goes Wilt is probably still the strongest player to ever plaer. If you dont think that is true spend a little time looking on the net. Wilt had the strength the body up even Shaq and in fact was probably stronger the him. And, there is no doubt as to who the better athlete was.
Now, if we are talking about the ability to take a hit only then that is a different topic altogether but it sure isn't Maxiel.