coup de grâce

 
Pronunciation: /ˌkuː də ˈgrɑːs, ku də gʀas/

noun (plural coups de grâce pronunc. )

  • a final blow or shot given to kill a wounded person or animal: he administered the coup de grâce with a knife
  • an action or event that serves as the culmination of a bad or deteriorating situation: Howarth delivered the coup de grâce with a penalty two minutes from time

Origin:

French, literally 'stroke of grace'