The Chieftain (Telnarian Histories (1))

A peasant is sent to the arena, fodder for the carnage but before the horrified gaze of noble ladies, the warrior named Dog slaughters headsmen, hunters, and beasts to win freedom as a full fledged gladiator. Then deep space rebels attack an Empire ship where Dog performs combat killings for the amusement of the passengers, and the gladiator becomes a rebel. Now a beautiful officer of the court finds her life depends on the mercy of Dog, the man she ordered put to death!