I don't think it's too farfetched to say their hardest punch was about the same. A common KO opponent for both as mentioned was Golota, and Lennox crushed him alittle quicker, however Tyson had more one punch KOs, so each fighter clearly deserves to be up their as the hardest punchers who ever lived. I think if each of them was told to throw their hardest punch and it was somehow scientifically measured, they would be pretty much equal.