Arch-nemesis

An archenemy, archfoe, archvillain, or nemesis (sometimes spelled arch-enemy, arch-foe, or arch-villain) is the principal enemy of someone or something. In fiction, it is a character who is the hero/protagonist's worst enemy.

The word 'archenemy' or arch-enemy originated around the mid-16th century, from the words arch- (from Greek "arkhos" meaning "most important") and enemy.

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