That's the last straw.
That's the last straw.
The expression "That's the last straw" stems from a longer saying which suggests that a small, additional burden can be decisive in making an unbearable situation intolerable. It's used when a series karma or accumulated grievances finally leads to a definitive reaction.
He always forgets my birthday; that's the last straw.
The speaker is fed up because someone always forgets their birthday, and they've reached their limit.
After all these issues, that's the last straw; I'm done.
The speaker has had enough after numerous issues and decides they are done.
I've been patient, but your continuous lateness is that's the last straw.
The speaker has been patient, but continuous lateness has been the final thing they can tolerate.