nuclear button

noun2

1. •
   The means (not likely literally a button) of quickly and easily launching nuclear warheads.

   • Reportedly, as Yeltsin accepted the need for bypass surgery he at first considered delegating responsibility for security to Premier Chernomyrdin, but retaining the nuclear button. — 2019
2. •
   The means of triggering a huge controversy, fight, or act of destruction.

   • The four left the meeting and in their absence the nuclear button was pushed. A daring plan was hatched to fully underwrite Ireland's entire banking network. — 2012