From that list I'd say Shavers then Foreman then Liston. All time I'm gonna go against the usual candidates and say Tommy Morrison. I specifically recall Magna saying that of all the people he talked to the hardest left puncher was "far and away" Morrison and this would include Tua. So yah Morrison. I've seen fights where his jab landed with such an impact and made such a sound it looked more powerful than Tyson's greatest hooks.