Antagonist

/æntˈæɡənˌɪst/

/ænˈtæɡənəst/

Antagonist

someone who strongly opposes another person or thing

synonyms : adversary

antonyms : agonist

a drug that neutralizes or counteracts the effects of another drug

antonyms : synergist

a muscle that relaxes while another contracts

Examples

1. Does the protagonist ever truly defeat the antagonist?

2. The antagonist was the Kessler syndrome and the propagation of orbital debris.

3. When one muscle contracts, its antagonist is stretched out.

4. We're fighting antagonists everywhere.