Re: Hearns is undoubtedly the hardest WW hitter or...
Robinson could do that too. He could also do it with a hook, an uppercut (from either hand) or just about any other punch except the jab.
As NWS said, his list of KOd scalps above 147 shows just how great his power was when at his prime weight. You can also see him as an amateur fighting well below 147 and knocking those poor kids clear across the ring and into bolivian and see he was always a monster.