My mettle defied by your licentious coup de grace of our love
Coup de grace (noun)
Merriam-Webster
A deathblow or death shot administered to end the suffering of one mortally wounded; a decisive finishing blow, act, or event
Licentious (adjective)
WordThink
Promiscuous and unprincipled. Lacking moral discipline
Mettle (noun)
The New York Times
The courage to carry on