The first two that pop into my head are James Toney and Jorge Castro... I might even rank Jorge Castro a little bit higher than Toney as Toney also had a phenominal defense to rely on avoiding KOs, Castro on the other hand was all chin and iron will. I'm a tad bit surprised that this guy isn't brought up more often. Fought from jr. middleweight all the way to cruiserweight and the only two people that could stop him was Juan Carlos Gomez and some CW named Jose Louis Herrera.. who has a perfect KO percentage.
Hagler took the cleanest punches and stood up to them. I think he could have taken Julian Jackson's punch.
:think I dare say NOBODY could have taken a clean Jackson punch. Much too devstating. Hagler has a legendary chin though.
George Chuvalo . . . tough sob! Haglar next, he was like a tank if anyone could have taken a clean punch from Jackson it would have been him. He took John "the beast" Mugabi', and Tommy Hearn's cleanest shots and it did not even make him blink.
Castro's chin was immense, but I do not believe it was the best ever. The best chins I have ever seen were Toney, Hagler, Oliver McCall, Chuvalo and Wayne McCullough. LaMotta too judging by written accounts. I've only seen two of his fights so I can't include him on my own list on the basis of such little evidence.
Chin is the most interesting aspect of boxing IMO. It really is inexplicable how a guy like Wayne McCullough, a small man and good but certainly not great boxer, is gifted with an incredible ability to take a punch, while other guys like Thomas Hearns, a big man at the weight he fought at and a great boxer, did not have resistance in any way comparable.