death blow

1. A hit or impact that causes immediate death. The warrior swiftly dealt a death blow to his adversary on the battlefield. When my husband was away fighting in the war, I worried constantly about him receiving a death blow. Everyone thinks they're skilled in battle until they're dealt a death blow.

2. An event that causes the abrupt end of something. His arrest and subsequent conviction was a death blow to his successful career as an attorney. Despite the company's recent success, the massive recall proved to be its death blow. The scandal over tax evasion will no doubt be a death blow to the senator's hopes for reelection.

a death blow

If something is a death blow to a process, situation, or organization, it causes it to end or fail. This could deal a death blow to the collapsing national economy. They warned that the deportations would be a death blow to the peace process.