antagonist

plural antagonists

1. An opponent or enemy.

   our antagonists in these controversies

   [1594], Richard Hooker, edited by J[ohn] S[penser], Of the Lawes of Ecclesiastical Politie, […], London: […] Iohn Windet, […], →OCLC, (please specify the page)

   2 more examples

   Antagonist of Heav’ns Almightie King

   1667, John Milton, “Book IX”, in Paradise Lost. […], London: […] [Samuel Simmons], and are to be sold by Peter Parker […]; [a]nd by Robert Boulter […]; [a]nd Matthias Walker, […], →OCLC; republished as Paradise Lost in Ten Books: […], London: Basil Montagu Pickering […], 1873, →OCLC

   [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, Edward Bulwer[-]Lytton, “A King in His City Hopes to Recover His Realm—A Woman in Her Chamber Fears to Forfeit Her Own”, in The Last of the Barons, London; New York, N.Y.: George Routledge and Sons […], →OCLC, book XII (The Battle of Barnet), page 433, column 2

2. One who antagonizes or stirs.
3. biochemistryA 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.

   2001: The calcium antagonists represent one of the top ten classes of prescription drugs in terms of commercial value, with worldwide sales of nearly $10 billion in 1999. — Leslie Iversen, Drugs: A Very Short Introduction (Oxford 2001, p. 41)

   Synonyms: blocker

4. authorshipThe 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, Will Wood (musician), “The Main Character”, in In case I make it,, performed by Will Wood

5. anatomyA muscle that acts in opposition to another.

   A flexor, which bends a part, is the antagonist of an extensor, which extends it.