assistant,
helper,
help,
supporter a person who contributes to the fulfillment of a need or furtherance of an effort or purpose; "my invaluable assistant"; "they hired additional help to finish the work"
accomplice -
An associate in the commission of a crime; a participator in an offense, whether a principal or an accessory.
Wikipedia
At law, an accomplice is a person who actively participates in the commission of a crime, even though they take no part in the actual criminal offense. For example, in a bank robbery, the person who points the gun at the teller and asks for the money is guilty of armed robbery. However, anyone else directly involved in the commission of the crime, such as the lookout or the getaway car driver, is an accomplice, even though in the absence of an underlying offense keeping a lookout or driving a car would not be an offense.
OmegaWiki Dictionary
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accomplice An associate in the commission of a crime.
