I agree with most of the names already mentioned. Im surprised noone said Trinidad. @ 147 if he caught you flush you were walking on black ice in tennis shoes immediately!
Julian Jackson. Hardest puncher, hardest p4p puncher whatever the category is of hardest puncher he wins. First guy I have ever seen put someone to sleep with one punch while the person was still moving.
in picking i consider those who was knocked out or down when caught with the punch, i go with mike tyson. come on, he knocked out/down heavyweights larger than he is.
Julian Jackson followed by Thomas Hearns..
when jackson was fighting u didnt have to worry about 10 counts, he put fools down for the weekend.
archie moore, bob foster and ray robinson deserves to be noted aswell. nobody mentioned them yet.