George Foreman
George Foreman
and Earnie Shavers

honorable mentions:

Ron Lyle (floored Foreman 3 times I think, not via george's exhaustion but with sheer power punches early in the fight when Goerge was still fresh as a daisy)

Rocky Marciano (cocksucker would hit someone and good night...except for ol' Don of course, that mofo may have had the best chin ever in boxing --- made Rocky look bad!)

Lennox Lewis (completely blew away fighters with single shots)