General Antonyms:
* Ally: Someone who works with you towards a common goal.
* Supporter: Someone who advocates for you or your cause.
* Friend: Someone who is close to you and has your best interests at heart.
* Teammate: Someone who is on your side in a competition or game.
Specific Antonyms:
* Proponent: Someone who argues in favor of something, the opposite of an opponent who argues against it.
* Advocate: Similar to a proponent, someone who actively supports a cause.
* Collaborator: Someone who works with you towards a common goal, similar to an ally but with a stronger emphasis on working together.
Other Options:
* Champion: Someone who fights for a cause or person.
* Supporter: Someone who gives their approval or assistance.
The best antonym to use depends on the specific situation and the meaning you want to convey.