After proving himself in two separate timelines during Dragon Ball Z, Dragon Ball GT makes it official that Trunks is the greatest all-around fighter.
There are a number of fighters within the world of Dragon Ball who are extremely powerful and worthy of praise, but Trunks is easily the greatest all-around fighter–and Dragon Ball GT proves it.
The first time fans were introduced to Trunks, he was actually an alternate version of a character who hadn’t even been introduced yet. Trunks is the son of Vegeta and Bulma, but that wasn’t immediately obvious upon his debut. Fans met a Trunks from an alternate future who traveled back in time to warn the Z-Fighters of the impending threat of the Androids, and then again to train with them to stop the Androids and Cell before they wrecked this timeline just as they did his. During the Android Saga, Bulma gave birth to the Trunks of the prime DBZ timeline–though it wasn’t until well after the Cell Saga that fans got to see this version of Trunks in action. Even as a little kid, Trunks showed immense power and fighting ability, so much so that he and Goten were recruited to battle Majin Buu when no one else was strong enough to. Future Trunks was strong to be sure, but the main timeline Trunks showed promise beyond anyone’s expectations–and he only became more impressive in GT.
In Dragon Ball GT season 1, episode 5 (written by Masashi Kubota, directed by Osamu Kasai, produced by Toei Animation), Goku, Pan, and Trunks are traveling the universe, searching for the Black Star Dragon Balls when they find themselves stranded on a world run by a cruel dictator.
The Dragon Ball heroes crash-landed on this world because a little piece of the spaceship that was accidentally kicked loose by Pan fell off upon takeoff. Evidently, that piece ended up being instrumental to the overall function of the spacecraft, so after some time without it, the whole ship stopped working and sent the team plummeting down towards the nearest planet. However, by the end of this episode, Trunks has gathered all the parts he needed, replaced the missing piece with a comparable one he found on this alien planet, and essentially rebuilt the ship perfectly.