Dempsey was up there...but let's not forget Louis. He was great at mixing the focus of his attack up between the head and body. Ever see that fight...I think it was vs. Walcott where the fighter he's attacking just wilts from the body assault....
Dempsey and Louis were obviously the most balanced and complete punchers of all the heavyweight champions IMO...they had mental strength, cool headedness, skill, an unflinchingly winning attitude, and were passionate about fighting. But they were also incredibly adept body punchers.