final/last straw

the final/last straw

the last in a series of unpleasant events which finally makes you feel that you cannot continue to accept a bad situation. One night he came home drunk at 5 o'clock in the morning and that was the last straw. He'd been unhappy at work for a long time but the last straw came when he was refused promotion. Lucy leaving was the last straw for him and he pretty much gave up the will to live. (often + for)

See also: final, last, straw