Along with unbelievably hard punchers, massive fighters like Paul Williams or Hearn's at the lower weight classes or granite chinned fighters like Chuvalo and McCall there's the particular freak of nature in boxing who can carry their power up several weight classes. Guillermo Jones is a package deal. A 6'4 former welterweight with one punch KO power who's fought all the way up to heavyweight and cruiserweight, keeping serious power the entire time. He recently broke down and stopped Firat Arslan, a tough, tough ******* in his own right.
Langford is the best example he was a knockout artist at every weight he fought at same with Fitzsimmons.
Langford, Fitz, Walcott are probably the top 3. I don't know if any welterweight could knock Gene Fullmer out with a single blow like Robinson did. Hearns and Trinidad both carried their power up well in weight. Arguello is up there, 5-1 (5) in title fights at feather, 9-0 (8 at Jr.Light, and 5-0 (4) at light. He also stunned Pryor on a few occasions at 140.
Ketchel deserves a mention. KD's Johnson and KO'd Dan Flynn (who admittedly wasn't a heavyweight at the time, but fought as one later on) faster than anyone but Dempsey and Fulton.
Roy knocked out no one worth mentioning at LHW. But at middle and SMW, without a doubt. He sparked a guy in two that went the distance with a late career Julian Jackson! :scaredas:
Hill and Griffin not worth mentioning? I'd add: Pacquaio: flyweight to lightweight Duran: bantamweight-light middleweight Patterson: Middle-HW Moore/Charles: MW-HW Hamed: flyweight-featherweight
Maybe Henry Armstrong? I don't have the exact numbers of KO's relative to which weight classes that he fought in, so I might be wrong.
Georges Carpentier's right hand was a good one for a small light heavy (maybe more suited to super-middle?) he starched a few heavies in his day and had the iron-jawed Jack Dempsey reeling for a few seconds with one shot aswell so he certainly carried the power up with him - he also competed either at national, European or world title level in all 8 divisions over the course of his career too