noun, noun-modifying (irregular)
Used in literary, dramatic, or narrative contexts to refer to a character who opposes the protagonist. Also used in pharmacology for a substance that blocks a biological receptor.
この小説のアンタゴニストは非常に魅力的な悪役だ。
The antagonist in this novel is a very compelling villain.
その薬
The drug acts as an antagonist of dopamine receptors.