Antonym of ACCOMPLICE

Accomplice : a person who helps another commit a crime.
Friend : a person with whom one has a bond of mutual affection, typically one exclusive of sexual or family relations.
Accessory : a thing which can be added to something else in order to make it more useful, versatile, or attractive.
Escort : a person, vehicle, or group accompanying another for protection or as a mark of rank.
Opponent : someone who competes with or opposes another in a contest, game, or argument.

Antonym of Accomplice is Opponent