General:
* Reunification
* Reunion
* Agreement
* Compromise
* Settlement
* Resolution
* Harmony
* Peace
* Amity
More specific:
* Conciliation (emphasizes the process of bringing parties together)
* Mediation (involves a third party helping to resolve conflict)
* Atonement (emphasizes making amends for wrongdoing)
* Forgiveness (emphasizes releasing resentment)
* Healing (emphasizes restoring a relationship to health)
* Reconcilement (an archaic synonym for reconciliation)
The best synonym for "reconciliation" will depend on the specific situation you are describing.