the.com/last gasp

means The final, most desperate effort made at the very last possible moment, when every other option has run out.

from Literal from the start — a gasp is the body's last grab at air before it gives out. The phrase has meant 'the point of death' since medieval times, and by the 1500s people were already stretching it figuratively to mean the final moment of anything — a battle, a cause, a deadline — not just a dying breath.