There are two versions of Trunks that have existed within Dragon Ball canon, and after both versions went on two nearly identical missions–one in Dragon Ball Z, the other in Dragon Ball GT–it became clear which of the two was better as one succeeded where the other so miserably failed.
The first version of Trunks fans are introduced to was Future Trunks who came back in time to help the alternate versions of his friends and family in the past to fight the Androids to protect their future from total annihilation. When Future Trunks was fighting alongside the Z-Fighters of the main DBZ timeline, his alternate self was just a baby. Fans wouldn’t see that version of the character in action until the Majin Buu Saga–and his power level didn’t disappoint. Trunks of the main Dragon Ball timeline (who will be referred to simply as ‘Trunks’) displayed incredible power for his age, more so than Goku or Gohan did at that same point in their lives. Trunks was something of a prodigy alongside his best friend, Goten, as the two of them could go Super Saiyan at an incredibly young age, could achieve fusion, and could even go Super Saiyan 3 while in their fusion state: Gotenks. All-in-all, it seemed as though Trunks would surpass his future counterpart as that version of the character couldn’t even break through the barrier of Super Saiyan 2 when he was close to adulthood. However, as Trunks got older, he evidently started to slip as he became a way worse warrior than Future Trunks–and one mission proves it.
In Dragon Ball GT season 1, episode 22 (written by Aya Matsui, directed by Osamu Kasai, produced by Toei Animation), the villainous Dr. Myuu reveals his evil plan to conquer the universe–that is, he reveals the being he was going to use to conquer the universe: Baby. Baby is a Machine Mutant within GT continuity with the power to possess people and steal their power/life force. In terms of abilities, aesthetic, origin, and motivation, Baby is essentially a mixture of Cell and Majin Buu–and his power level reflects that as well. In this episode, Baby is still little more than an artificial fetus growing in a tank, and before Myuu revealed Baby to the Z-Fighters, Trunks snuck into his chamber and uploaded a virus into the growing tank–one which promised to kill Baby before he was ever ‘born’. Unfortunately, Trunks’ plan doesn’t work and Baby proved stronger than the virus. Baby was born, and he didn’t waste any time attacking those around him with the goal of eventually conquering the universe–something that was very-much within his reach based on his unparalleled power level.
Trunks Nearly Ended the Universe by Not Following the Footsteps of Future Trunks
In Dragon Ball Z, when Future Trunks was with the Z-Fighters of the past, and they were going up against the Androids and Cell, he and Krillin tracked down the secret laboratory where Cell was being grown, and the two of them obliterated it completely. Future Trunks knew how dangerous Cell would become if he was allowed to live, so in order to keep this planet safe, he left no trace of Cell whatsoever–which is exactly what Trunks should have done with Baby.
Trunks in Dragon Ball GT is the main timeline Trunks all grown up, but apparently he didn’t grow up with the same common sense as his future counterpart. Rather than using his ki to decimate Baby’s growing chamber–given the threat the villain poses to the entire universe–Trunks uploads a virus into his tank, a method that always had the potential to fail. Future Trunks took no chances and destroyed Cell completely, thereby ensuring the safety of the main Dragon Ball Z timeline and proving that he’s way better than his Dragon Ball GT counterpart by successfully completing essentially the same mission Trunks utterly failed.
