Kessler is a three time world champ at 168, and two of those titles were won during a very flat-footed portion of his career.
:good You could put Joe's bottom half in a potato sack and he'd still be effective against just about every other HW in history.
Gene Fullmer Jack Johnson Joe Louis Jack Dempsey moved kinda flatfooted to me, quick but flat footed Mike Tyson was flatfooted alot because he was planting to either used head movement or throw punches. He was so quick closing the distance that he wasn't on his toes too long The two most famous Rockys, Marciano and Graziano fought flatfooted.....and so did Jake Lamotta now that you mention great Italian-American boxers Butterbean and Balboa were flatfooted too.....just kidding
Pavlik tops my list. He just stands there trading. Arreola prob makes the list also. One thing about this style is it's super entraining to watch.