(Greek mythology) The goddess of divine retribution.

(astronomy) 128 Nemesis, a main belt asteroid.

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

(chiefly Canada, US) An enemy, especially an archenemy.

(chiefly outside the US and Canada) 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.

The principle of retributive justice.

(usually in the singular, formal) A punishment or defeat that is deserved and cannot be avoided; (an instance of) retribution.