David Tua Razor Ruddock Joe Frazier Tommy Morrison Floyd Patterson Patterson and Frazier were the two lightest guys. Morrison only kod weak opposition or very faded guys with the left hook. I think Frazier's was the best for consistency, if not the hardest.
Tua also had a very good right hand which ko'd some opponents , Frazier did not. Power and chin are pretty important assets,imo.