the final/last straw idiom (also the straw that breaks the camel's back)
C1 （压垮骆驼的）最后一根稻草；使人最终崩溃的一击
the last in a series of unpleasant events that finally makes you feel that you cannot continue to accept a bad situation
Losing my job was bad enough, but being evicted was the final straw. 丢了工作已经够糟了，但被房东赶出门后我彻底崩溃了。
She's always been rude to me, but it was the last straw when she started insulting my mother. 她一直对我很粗鲁，但让我终于无法忍受的是她竟然开始辱骂我的母亲。