I'd actually go with Cooney. Not as good as Wlad, not as talented as Wlad, and didn't have the technique Wlad had, but for pure power his left hook was murderous. Cooney is the only guy who legitimately wobbled Foreman during his comeback. Marciano is without question far and away the GOAT of white heavyweight punchers.
Holyfield wobbled Foreman a few times. I'd rank Wlad higher than Marciano as a puncher, and a heavyweight.
Klitschkos left hook is harder than anything Cooney mustered. Who did Cooney crack with the hook? Old Norton, Old Lyle and Old Young. Klitschkos late round power in the left was evident against guys who had way more left in their tanks than those guys had. Chambers, Peter, Pulev, were all undefeated and either taken out or dam near taken out off single left hooks. Shufford was laid out by a single hook. Clusters dropped Mercer, never down off a head shot till then. Ditto Ray Austin. Cooney knocking out aged chinny guys...no chance.
One of the hardest. It's worth bearing in mind that Schultz and Stewart lumped up Foreman pretty good. Cooney was a vrackhead by the Foreman fight and albeit he managed to give George a black eye he never had a shout in that fight.
I'd say Wlad, in all honesty. He had the frame, size, athleticism and technique to generate huge power. Proper crunching shots. It's a shame he would rather impersonate an overly-affectionate octopus.
Wlad is definitely up there but Corrie had this FAAAST left cross that I'm not sure if Wlads right was harder than...
