Here's the current heavyweight active boxers and the number of world titleholders they have beaten (not counting interim titles, and just the 4 major sanctioning organizations).
Evander Holyfield (15): Tyson x 2, Qawi x 2, Rahman, Ruiz, Moorer, Mercer, Bowe, Holmes, Foreman, Douglas, Parkey, Ocasio, De Leon
Wladimir Klitschko (8): Byrd x 2, Peter, Mercer, Brewster, Chagaev, Ibragimov, Rahman
Vitali Klitschko (5): Hide, Sanders, Peter, Gomez, Norris
David Haye (5): Valuev, Ruiz, Maccarinelli, Fragomeni, Mormeck
David Tua (4): Ruiz, Maskeav, Rahman, Moorer
Nicolay Valuev (3): Ruiz x 2, Holyfield
Sam Peter (3): Toney x 2, Maskaev
JC Gomez (3): Dominguez, Castro, McCall
Jean Marc Mormeck (3): Hill x 2, Bell
Oliver McCall (3): Akinwande, Maskaev, Lewis
Hasim Rahman (2): Lewis, Sanders
Shannon Briggs (2): Lyakhovich, Foreman
Oleg Maskaev (2): Maskaev x 2
Sergey Lyakhovich (1): Brewster
Alexander Povetkin (1): Byrd
Eddie Chambers (1): Peter
Lamon Brewster (1): W. Klitschko
Robert Helenius (1): Brewster
Kevin Johnson (1): Seldon
Danny Williams (1): Tyson
Evander Holyfield (15): Tyson x 2, Qawi x 2, Rahman, Ruiz, Moorer, Mercer, Bowe, Holmes, Foreman, Douglas, Parkey, Ocasio, De Leon
Wladimir Klitschko (8): Byrd x 2, Peter, Mercer, Brewster, Chagaev, Ibragimov, Rahman
Vitali Klitschko (5): Hide, Sanders, Peter, Gomez, Norris
David Haye (5): Valuev, Ruiz, Maccarinelli, Fragomeni, Mormeck
David Tua (4): Ruiz, Maskeav, Rahman, Moorer
Nicolay Valuev (3): Ruiz x 2, Holyfield
Sam Peter (3): Toney x 2, Maskaev
JC Gomez (3): Dominguez, Castro, McCall
Jean Marc Mormeck (3): Hill x 2, Bell
Oliver McCall (3): Akinwande, Maskaev, Lewis
Hasim Rahman (2): Lewis, Sanders
Shannon Briggs (2): Lyakhovich, Foreman
Oleg Maskaev (2): Maskaev x 2
Sergey Lyakhovich (1): Brewster
Alexander Povetkin (1): Byrd
Eddie Chambers (1): Peter
Lamon Brewster (1): W. Klitschko
Robert Helenius (1): Brewster
Kevin Johnson (1): Seldon
Danny Williams (1): Tyson
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