the final nail in the coffin

US /ðə ˈfaɪnl neɪl ɪn ðə ˈkɔfɪn/
UK /ðə ˈfaɪnl neɪl ɪn ðə ˈkɔfɪn/
"the final nail in the coffin" picture
1.

最后一根稻草, 致命一击

an event that causes the failure of something that had already been weakening

:
The company's latest scandal was the final nail in the coffin for its reputation.
公司最新的丑闻是其声誉的最后一根稻草
His decision to quit was the final nail in the coffin for the struggling project.
他辞职的决定是这个陷入困境的项目的最后一根稻草