Longman Dictionary of Contemporary English
death blow
noun
EXAMPLES FROM CORPUS
▪ Neither, however, will be a death blow.
▪ The death blow to drug chic actually may have been struck by a fast-food chain.
▪ The death blow to the Aksumite kingdom came in the tenth century from unassimilated Agaw in the south.
▪ The fact that they have seen nothing is by no means an immediate death blow for all grand unified theories.
▪ Was it however so paradoxical as to have dealt a death blow to the theory?
Usage examples of "death blow".
He'd let her crawl, limp, stumble the entire length of the fourth-floor corridor before he delivered the death blow.
Blood had trickled and dried on the hair and skin of the temple, running there from where she could see the death blow at the back of the head.
However, the death blow was inflicted at close range, and there is no evidence of struggle, duress, no defensive wounds.