The phrase "clinched the deal" signifies that an agreement or negotiation has come to a successful conclusion. Antonyms for this phrase could include "failed to secure the agreement", "lost the deal", or "fell through at the last moment". Other antonyms could include "negotiated poorly", "couldn't reach a compromise", "left the table empty-handed", or "couldn't seal the deal". These antonyms demonstrate the range of possibilities when it comes to negotiations, and highlight the importance of strategy and communication in securing a successful outcome. While the phrase "clinched the deal" is often associated with success, it is important to remember that not all negotiations result in a positive outcome, and that sometimes it is necessary to walk away without an agreement.