The last/final straw
Definition 1 of 1
Pro Tip 1/3Emotional Intensity
Expresses strong emotion after tolerating many problems. Shows you've reached your limit. 
After weeks of overtime, the server crash was the last straw for me.
Pro Tip 2/3Breaking Point
Indicates a specific moment where things become too much to handle, not just any frustration. 
She was patient with the delays, but the lost shipment was the final straw.
Pro Tip 3/3Sequence of Events
Used after a series of negative events, not just a single incident. 
The team's laughter at my idea was the final straw after their constant teasing.