> To be the last in a sequence of unpleasant things
> To be the last tolerable thing after which something cannot be accepted
This is the shortened version of the phrase the last straw that broke the camel’s back. The phrase has been used since the mid 1700s. The phrase has had many variations over the years. There is an earlier phrase dating back to the 1800s that states the last feather breaks the horse’s back.
Example
The last straw in their relationship was when he physically abused her. She walked out after that.
I am not going to wait for the last straw like you always do. I will do something about the problem much sooner than that.