Who are the biggest punchers each of these heavyweights defeated?

Yes, Tyson was still a hellacious puncher, though most of his other skills had eroded by then.

 

Would rate it:

1. Lewis
2. Wlad
3. Bowe
4. Liston/Frazier
5. Marciano/Dempsey

 

Tyson's heavy handedness is often overlooked, but he actually notched a number of his best and cleanest one punch KOs near the end of his career. He was definitely still capable of stopping almost anyone if he could land on them; the problem was, his other skills had eroded to the point where he was no longer able to make that happen with the type of freakish inescapability of his prime incarnation.

 

Hide, Cooper, Seldon and Golota were better punchers either Frazier or Liston faced.
Liston had Patterson and Williams, Frazier had Bonavena and Foster.

I think Hide is extremely underrated in therms of sharp powerful punching as well as a fighter in general. He only failed vs. SHW toughness.