In both the original Dragon Ball series and the sequel series Dragon Ball Super, Trunks has made a name for himself, not just as the half-Saiyan son of Vegeta, but as the time traveling hero who will go out of his way to save the lives of his family even if it doesn’t impact his future timeline. While Trunks is perhaps the most popular time traveling warrior in Dragon Ball, he certainly isn’t the only one, and the other warrior in question isn’t anywhere near as heroic.
Trunks made his debut in Dragon Ball chapter 331 by Akira Toriyama. In that chapter, Trunks is shown facing off against Mecha Frieza, though at the time, no one knew his true identity or intentions. Regardless of who he was, however, Trunks proved how immensely powerful he was by killing Frieza like it was nothing–something that happened immediately following the Frieza Saga in which Frieza was thought to be the most powerful force in the galaxy. When the Z Fighters saw Trunks kill Frieza so brutally, they were immediately intrigued and intimidated, though the intimidation factor lessened when Trunks approached the heroes with a kind smile and no semblance of aggression. When Trunks explained himself, it was revealed that he was from an alternate future, and he traveled back in time to warn the Z Fighters of the impending Android threat. Unfortunately, his meddling with the time stream also brought back something far worse.
In Dragon Ball chapter 363 by Akira Toriyama, Piccolo is facing off against the villainous Cell who was in the middle of draining regular humans of their life force to make himself stronger. When Piccolo feigns an injury, he convinces Cell to explain who he was and how he came to be here. Cell tells Piccolo that he is from the future, and he only traveled to the past so that Cell could absorb Androids 17 and 18 in order to reach his perfect form. In the future Cell is from–which is only a little later than the future Trunks traveled from–17 and 18 were killed by Trunks, so he wasn’t able to absorb them. After Cell killed the future version of Trunks, he stole his time machine and went back to the alternate past of Dragon Ball’s present.
The thing about time travel in the Dragon Ball universe is that none of the changes made in the past impact the future. So, when Trunks went back in time originally to warn the Z Fighters about the Androids, the future he returned to remained unchanged, and he actually created an entirely new timeline by taking that trip to the past. What’s worse, is that Trunks’ time machine saves and records those trips to the alternate timeline, meaning anyone who hops into the machine can use it without really knowing how to use it. After the distant future version of Trunks was killed by Cell, this is exactly what happened, leading to a villain from an entirely different timeline threatening the lives of the Dragon Ball heroes of the present.
What is interesting is that, just as Trunks also existed as a baby in the present day, there was also a version of Cell who was only little more than an inorganic fetus growing inside a lab originally operated by Dr. Gero–the creator of the Androids. This means that the Z Fighters would have had to deal with Cell eventually, but Trunks opened the door for Cell to be an immediate problem while also being the sole solution to the problem that he technically created. Obviously, time travel stories are always a bit confusing, but the main takeaway here is that Trunks isn’t Dragon Ball’s only time traveling warrior, as he shares that honor with Cell.