Idiom
final strawthe 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)