If we are talking pure power then the not exactly reknowned Andy Ganigan comes into the debate as some have stated. He just hasn't got much substance resume wise.
In terms of one punch power.... Young Otto....record for 1 rd kos Benny Leonard-great 2 hand puncher Charlie White-great left hook artist Ruby Goldstein-Floored almost everyone he hit-Glass chin Al Bummy Davis-hardest left hook I ever saw-kod Mongomery in one Ike Williams-vicious 2 hand puncher-uncuffed
Pure power - not resume or delivery system Billy Petrolle Roberto Duran Edwin Rosario Andy Ganigan Edwin Valero would be my picks strictly for lightweights - there are some I rate at other (close) weights that might deserve a place... Like Henry Armstrong
Petrolle is an odd one IMO. He dosent strike me as someone who you would call a great pucnher. To me he was a strong puncher who would look to wear you down with pressure and body work but not really a big puncher in his own right. Maybe someone could disagree with me and explain why they have picked him?
Petrolle is someone I consider aswell Greg but I thought his numbers were a tad deceiving at first glance..call it ignorance, as Im not all that familiar with him but his Ko percentage seemed a little inflated because a lot of his knockouts came against his lesser opposition. Ill admit I didnt look at it throughly but it seemed the better opponents he fought and beat went the rounds with him. And coincidentally I found an article claiming Berg was sick for the fight Petrolle stopped him in. He is certainly a puncher but how big compared to the other mentioned I dont know.
To me on film he looks a strong wear you down puncher, not what I would call a 'top 5 puncher'. Think Carmen Basilio type. Although you could argue that him going rounds against the better opponents Canzoneri, Berg etc... is due to them being the level above him, and not due to his lack of power.