General antonyms:
* Harmony: A state of peaceful agreement and understanding.
* Peace: A state of tranquility and freedom from disturbance.
* Agreement: A state of mutual understanding and acceptance.
* Concord: A state of complete agreement and harmony.
* Unity: A state of being united or joined together.
* Cooperation: The process of working together to achieve a common goal.
Antonyms related to specific aspects of quarreling:
* Reconciliation: The act of restoring friendly relations after a disagreement.
* Compromise: A settlement of differences by mutual concession.
* Understanding: A state of comprehension and empathy.
* Forgiveness: The act of pardoning someone for an offense.
* Acceptance: The act of acknowledging and receiving something without resistance.
The best antonym for "quarrel" will depend on the specific context in which it is used.