As used in law these words all convey the idea of complicity or common guilt in a wrongful act.
Confederate is the general term applied to any person who in conjunction with others intentionally contributes to the commission of an unlawful act, whether the act be a crime or a civil injury.
For civil joint wrongdoers the specific term is conspirator.
An accessory is neither the chief actor (principal) in an offense nor a person present at its performance but one who accedes to or becomes involved in its guilt by some act (as of instigating, encouraging, aiding, or concealing) either previous or subsequent to the commission of the offense.
In the case of certain classes of offenses (as treason or misdemeanors) the law ordinarily recognizes no distinction between an accessory and a principal.
An abettor is one who is actually or constructively present at the commission of the deed and contributes to it by moral or physical force.
An accomplice is one who with criminal intent participates in the commission of an offense whether as principal, abettor, or accessory.
Legal usage does not recognize the distinction made by laymen between principal and accomplice.