Elite Saiyan Warrior
Super Saiyan 2
He prevented the death and destruction caused by Majin Buu. In Dragon Ball Super, Future Trunks meets up with Goku and Vegeta and they discuss everything that's happened since Cell. Trunks explains, despite the difficulty, how he killed Dabura and Babidi, preventing the release of Majin Buu. There's no way Trunks was stronger than Goku at that point. It just shows that while Goku and Vegeta mess around, Trunks takes thing seriously. Probably a product of the world he grew up in. Either way, it seems that the whole Majin Buu thing could have been prevented had our Saiyan heroes took the situation a little more seriously.