I was gonna answer this thread with Ike Williams. People seem to think he was this mini Louis, this one punch knockout artist, despite the fact that his most famous footage shows him detonating about 40 full power bombs on a defenseless opponent who stays on his feet throughout all of it. He also didn't knock his opponent out in even half of his wins, but that's just as much a result of his style. He was a boxer first and foremost. Good puncher. Not one of the greatest. Not as far as pure power is concerned, anyway.
Ezzard Charles. He's KOed three ATGs: Archie Moore, Lloyd Marshall and Jimmy Bivins. He also 'almost KOed' granite chinned Charley Burley. He KOed top contenders like Anton Christoforidis, Oakland Billy Smith and Jose Basora. At HW he stopped the likes of Ray, Layne, Valentino and Barone. Comparing that to Moore, he stopped Marshall quicker (twice), he also stopped Bivins and Smith quicker. He only needed one punch to ice Satterfield, Moore needed loads. He's made a man go blind and killed a man. His KOs over Reynolds and Satterfield are two of the cleanest one punch KOs ever. All that, but only a 43% KO rate, since he fought a lot at HW, fought on wayyyyy too long and ultimately didn't really fight with all-out aggression and fought some of the best competition ever. I think he was just as dangerous as Moore or Foster when he sat down on his shots. And even if he wasn't, he hit harder enough to stop 95% of all light-heavyweights anyway.
Dick Tiger, Gene Fullmer, and Carmen Basilio were all powerful hitters but often won by decision. Ron Lyle could also certainly fit into this category.
I wouldn't say Liston, although he could win a decision. Patterson and Quarry were also very capable of winning on points.