antagonist

noun5

1. •
   An opponent or enemy.

   • [H]is eyes vacant—his face haggard—his head drooping, the spectacle of such an antagonist to the vigorous Edward, moved only pity in the few, and ridicule in the many. — 1843
2. •
   The main character or force opposing the protagonist in a literary work or drama.

   • So God forbid I'm seen just as an average human being / I mean, imagine if antagonists lacked any evil scheme — 2022
3. •
   A chemical that binds to a receptor but does not produce a physiological response, blocking the action of other agonist chemicals, such as endogenous chemical messengers.
4. •
   A muscle that acts in opposition to another.

   • A flexor, which bends a part, is the antagonist of an extensor, which extends it.
5. •
   One who antagonizes or stirs.