Win the indicated match in ESPN Classic Fights mode with the listed boxer to unlock the corresponding style:

Judge Jab: Defeat Joe Frazier with Muhammad Ali.
Lethal Uppercuts: Defeat anyone with Roberto Duran.
Sinister Cross: Defeat anyone with Roy Jones Jr.
Slickster: Defeat anyone with James Toney.
Textbook: Defeat anyone with Oscar De La Hoya.
Uptight, and Hard Straights: Defeat anyone with Winky Wright.