Foreman was very badly beaten up by Axel Schultz. Foreman won by an extremely controversial decision, so a rematch was ordered by the IBF. Foreman gave up the IBF title rather than fight a rematch with Schultz. Schultz had never been stopped, until Vladimir Klitschko stopped him in the 8th round. Tua at his prime was awesome. Foreman was at his best when he fought Frazier, but then along came Jimmy Young, Ali, etc. I have to pick Tua, his punches were faster and much more devastating..........
Foreman's power was 'universal', he could hurt you with any type of punch whether it landed perfectly or was slightly off and could hurt you with less than optimal technique as well, ie an arm punch that wasn't even 'on the button' could hurt you. To me that says his power was unreal. Tua had power but he needed to throw it properly for it to be devastating, that said his left hook was probably more powerful than Tyson,s but of course Tyson's raw power is a little overrated, it was his technique that made his punches so devastating ie the fact he could LAND his best punches with regularity as opposed to most power punches who can spend the whole fight 'looking for that one shot'.
Foreman had huge bludgeoning power. His body shots we're sickening, would hate to take one of those. Tua was more explosive and probably hit as hard with the left hook as any Foreman punch but he was a one handed fighter. I'd say Foreman was clearly the better puncher, greater variety and power in every punch even his jab. He also kept his power better than Tua. Even in his mid 40's he had one punch KO power while Tua now no longer seems to have the power he once had.