Sugar Ray Leonard. I'm not sure if I can call him the greatest but I think he was the greatest or the biggest puncher, p4p. Though I never liked him coz I never liked boxers who fool around too much on the ring and taunt his opponents; nevertheless, I couldn't help being amazed at his punching power. I think he could've knocked out just about anyone he wanted, even Marvin Hagler, if he just let loose those punches, but sometimes he just seemed to be tentative and just couldn't let it out, I think it's a question of his heart. You'll see his full power when you see him knocking out this Canadian (what's his name?) fighter.