nemesis

An enemy, especially an archenemy.

Batman is in constant conflict with his nemesis, The Joker.

The roofer stayed in touch, committed to the downfall of his nemesis, Mikey. One week after his initial phone call, we were on our way to raid Mikey's trite home armed with a federal search warrant. There were six of us.

A person or character who specifically brings about the downfall of another person or character, as an agent of that character's fate or destiny, especially within a narrative.

The personification of the "fatal flaw" of a dramatic hero in the style of Greek tragedy.

Polar opposite, especially of a literary character.

“And then, while he's devouring you with his stare, thinking about how much he wants to lick you up, along comes his antithesis, his polar opposite, his nemesis for want of a better word—” “Nemesis?” I interrupted, eyebrows journeying up my forehead. “—who swoops you off your feet and away from him,” Heather continued, ignoring my incredulous expression.

The principle of retributive justice.

The goddess of divine retribution.

128 Nemesis, a main belt asteroid.

A hypothetical star postulated to be orbiting the Sun to explain a perceived cycle of mass extinctions in the geological record.