"The final blow" is a phrase that is often used to describe the last and most decisive action that brings a situation or conflict to an end. Some synonyms for this phrase include "the coup de grace," which is a French term that is used to describe a lethal blow that finishes off a wounded animal or opponent. Another synonym is "the finishing blow," which refers to the last blow that seals the victory or defeat of a person or team. Other possible synonyms include "the knockout punch," "the death knell," "the closing shot," and "the decisive strike." These phrases can be used interchangeably to describe the last and most critical action in a situation.