P4P he would be top 10 somewhere this list isn't in order.

Earnie Shavers
George Foreman
Rocky Marciano
Mike Tyson
David Tua
Jack Dempsey
Joe Louis
Ike Ibeabuchi
Sonny Liston
Lennox Lewis

Also some other Heavyweights with devastating power.

Abe Simon
Buddy Baer
Gary Mason
Alex Stewart
Joe Frazier
Jim Jeffries
Frank Bruno
Razor Ruddock
James Bonecrusher Smith