I was going to vote for foreman because of his fight against moore, but then i thought of earnie shavers and the fight against ali, that's why it changed my mind.:good
How was that not a 1 punch KO? Marciano through that single right, it landed, and Layne was out cold for over a minute. http://www.youtube.com/watch?v=RP3UManJNsw
Shavers posessed the hardest single punch in the sports history, chilling raw power. Overall Tyson and Lewis were in that same bracket and had superior excecution on their shots, put combinations together better etc. Tua was also an extremely powerful hitter. If your talking just power, I'd say Earnie.
Talking about Tua, what about his destruction of Ruiz. Brutal knockout: http://www.youtube.com/watch?v=8AVh5TKS80M
I would have a hard time saying who had the most power, but when it comes to the combination of power, speed and accuracy I might just go with Tyson even if I don't rate him that highly.