deathblow

noun

Etymology: From death + blow.

1. A strike or blow that leads to death, especially a coup de grâce.

   “He was also there at that fight when Hygelac folded under his deathblow.”

   “Together we will finally strike a deathblow against the corrupt, bloated creature that is the so-called Republic.”

2. Something that prevents the completion, or ends the existence, of a project etc.; a fatal setback.

   “The opening of the bridge dealt a deathblow to the ferry.”