Which heavyweight was truly unbeatable for these years? Sonny Liston 1962-64 George Foreman 1972-74 Mike Tyson 1987-89
Out of the fighters listed I think Tyson overall beat more notable names and I think stylistically he would beat more notable Heavyweights past/present than either of the other 2 Heavyweights. So I'll go with Tyson.