General Antonyms:
* Oppose: To be against something.
* Deny: To refuse to acknowledge or accept.
* Refute: To prove something wrong or false.
* Disapprove: To have a negative opinion of something.
* Condemn: To criticize strongly.
* Reject: To refuse to accept.
Antonyms in legal context:
* Defendant: The person accused of a crime in a court of law.
* Opponent: The person who opposes another in a legal case.
Antonyms in political context:
* Opponent: A person who opposes a political candidate or party.
* Critic: A person who expresses disapproval or criticism.
Other possible antonyms:
* Ignore: To pay no attention to.
* Neglect: To fail to care for or attend to.
* Detract: To take away from the value or quality of something.
* Undermine: To weaken or damage.
The best antonym for "advocate" depends on the specific situation and what you are trying to convey.