The straw that broke the donkey's back phrase
Used to allude that the last force, problem or burden which is seemingly minor and small causes a person, system or organisation to collapse or fail
That lie was the straw that broke the donkey's back and the boss decided to fire him.
Her husband's violent act last night was the straw that broke the donkey's back and she left him.
If something is more than flesh and blood can bear, endure, etc., it is unpleasant, painful, or offensive than one is able to tolerate or endure.
Put an end to a bad experience or situation in an especially negative way, usually a series of unpleasant events
I argued with my wife this morning and failing in negotiating with my customer has put the tin lid on my bad day.