Marciano and Foreman were both freaks of nature in terms of natural punching power; arguing who may or may not have hit harder is kind of a mute point. Chances are they could put anyone away if they got to them clean. Rocky's Susie Q was actually measured at hitting with 900+ lbs of force and I wouldn't doubt prime Foreman's best punch being close to that. These men were both monsters who were going to hurt you when they landed good.
(youtube fighting science in case you haven't seen it, I don't agree with all of it but it's worth a watch)
I've heard of guys like Bruno ,Lewis ,Tyson and shavers all hitting WELL over 1000 lbs of force, I'm sure Foreman could to.
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