At Hearns best, he was only beaten by SRL and Hagler. Both also happen to be ATG's. He fought an amazing fight against SRL before he gassed. Tho he went full ****** against Hagler. Do people not realize how tough it would be to beat a 6'4/6'5 Hearns that would probably have around an 84 inch reach? Did Rocky ever fight a guy with that reach? Hell, how many guys did he fight that were that tall?
Marciano had great heavyweight power? Since when? He never knocked out a heavyweight. You mean he had great power because he was white? If Archie Moore a chinny guy who was a natural middleweight could knock down Marciano then so could Hearns and Hearns was alot faster than Moore.
I don't see how your initial point about Hearns' chin is even controversial. Hearns is my favorite fighter of all time, but I have to agree with Hagler's claim while color commentating in the 2nd Leonard fight that "Tommy's got that weak chin." You have to be utterly delusional to not see this.