acrimony
Meaning: bitterness, discord
Usage: Though they vowed that no girl would ever come between them, Biff and Trevor could not keep acrimony from overwhelming their friendship after they both fell in love with the lovely Teresa.
rancor
Meaning: deep, bitter resentment
Usage: When Eileen challenged me to a fight, I could see the rancor in her eyes.
caustic
Meaning: bitter, biting, acidic
Usage: The politicians exchanged caustic insults for over an hour during the debate.
acerbic
Meaning: biting, bitter in tone or taste
Usage: Jill’s acerbic comment made the room fall silent.
vitriolic
Meaning: having a caustic quality
Usage: When angry, the woman would spew vitriolic insults.