Complex sentence: James "Buster" Douglas (born April 7,1960) is an American former professional boxer and undisputed world heavyweight champion, best known for scoring a stunning upset when he knocked out previously undefeated champion Mike Tyson on February 11,1990, in Tokyo.
Split into simpler sentences: James "Buster" Douglas (born April 7,1960) is an American former professional boxer. He held the undisputed world heavyweight title and is best known for scoring a stunning upset when he knocked out previously undefeated champion Mike Tyson on February 11,1990, in Tokyo.