Dragon Ball Super (2016), S01E060: Back to the Future - Goku Black's Identity is Revealed
With Zamasu defeated, Beerus is convinced that Future Trunks' timeline has become peaceful once again. Although hesitant, Future Trunks decides to go back to his timeline to make sure that is the case. Goku, Vegeta, and Bulma accompany him. As soon as they arrive, they realize that nothing has changed. Future Zamasu and Goku Black learn of Goku and the others' return. The two groups meet shortly after. Goku Black reveals himself to be Zamasu who had stolen another timeline's body of Goku with the wish granted by the Super Dragon Balls. Goku Black used its potential to grow stronger than Goku himself.