I am only listing five, from lightweight to heavyweight, based on boxing's original eight weight classes. And I am only mentioning fighters that I have witnessed on live television or in-person, to avoid the inevitable hate mail and comments that readers are bound to send in response to my totally subjective list.
My criteria is based largely on the boxer's "true knockout" percentage in all of his fights (at least 40). In case you were wondering, a true knockout is one where the victim does not beat the 10-count.
And without further ado, I announce the "five hardest-hitting men, from 135 pounds to unlimited, that I have ever seen in living color," including some vintage YouTube footage to scramble your brain cells.
George Foreman (True KO% 30.86). His greatest true knockouts were against Ron Lyle in '76 (OK, so I didn't see it live but the most exciting fight in heavyweight history was insane) and for the unified heavyweight championship against Michael Moorer nearly 20 years later.
Julian Jackson (True KO% 26.23). Pound-for-pound, arguably the purest puncher of the past 20 years. This guy literally seemed to be able to render an opponent senseless before he even hit the canvas.
Although his competition often was not the greatest, he was still a champion with lightning in his fists. Just ask former middleweight contender Herol Graham.
Thomas Hearns (True KO% 34.33). His nickname says it all. This side of Joe Louis, the "Hit Man" may have had the best overhand right in boxing history.
His knockout of Roberto Duran was not a true knockout, technically-speaking, but it's as close to the truth a knockout could be.
Diego Corrales (True KO% 24.44). "Chico" was the man. He's known mainly for his epic wars against Jose Luis Castillo as well as his one-sided TKO loss to Floyd Mayweather, Jr.
However, he was the hardest-hitting lightweight (130-135 lbs.) puncher that I have seen recently. I'm still mad at Acelino Freitas for depriving him of his true knockout when he quit in their lightweight unification bout.