I would say Earnie Shaver. It's hard answer though because Roy Jones hit like a mutha too, Ray Robinson KO'd people who'd seldom ever been down with one punch. Sam Langford was a damn beast. Ugh its just too large of a list to narrow down to a single hardest puncher ever considering we still don't have a good way to measure a boxers punching power (even though actual instruments to do that exist)

So let's leave it in theorycraft and discussions