Antonym of ADHERENT

Answer: Option C

Adherent : someone who supports a particular party, person, or set of ideas.
Rival : a person or thing competing with another for the same objective or for superiority in the same field of activity.
Alien : belonging to a foreign country.
Detractor : a person who disparages someone or something; critic.
Enemy : a person who is actively opposed or hostile to someone or something.

Antonym of Adherent is Detractor