spoiler

One who spoils; a plunderer; a pillager; a robber; a despoiler.

One who corrupts, mars, or renders useless.

A document, review or comment that discloses the ending or some key surprise or twist in a story, or the internal rules controlling the behaviour of a video game, etc.

(aeronautics) A device to reduce lift and increase drag.

(automotive) A device to reduce lift and increase downforce.

(US, chiefly politics, sports) An individual (or organisation etc.), unable to win themselves, who spoils the chances of another's victory.