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general::
Phrase(s): (another) nail in someone’s or something’s coffin
Fig. something that will harm or destroy someone or something. (Alludes to the sealing of a coffin with nails.) • Every word of criticism that Bob said about the boss was another nail in his coffin. • Losing their biggest customer was the final nail in the company’s coffin.
McGrawhill's American Idioms And Phrasal Verbs