Jimmie Foxx
Babe Ruth is the all-time leader with a career slugging percentage of .6897. Ted Williams (.6338), Lou Gehrig (.6324), Mule Suttles (.6179), Turkey Stearnes (.6165), Oscar Charleston (.6145), Jimmie Foxx (.6093), Barry Bonds (.6069), and Hank Greenberg (.6050) are the only other players with a career slugging percentage over .600.