Throughout his many appearances in the Dragon Ball mythos, Trunks has proven himself to be a true hero as he is always willing to put his own well being on the line and travel into the unknown if it means protecting his world and the people he loves. However, during his first mission involving a time machine and a fractured timeline, Trunks accidentally broke the Dragon Ball universe, but by doing so, he actually saved it.
Trunks is the son of Vegeta and Bulma who made his debut in Dragon Ball Chapter 330 by Akira Toriyama. The first time readers see Trunks, it is a version of the Saiyan hero from the future who traveled back in time to destroy the Androids before they became too powerful and decimated the world just as they did in his future. However, as Trunks later discovered, traveling back in time and changing events from the past doesn’t change the future. Instead, all of the timeline meddling Future Trunks did, while for the right reasons, skewed his timeline and effectively broke the Dragon Ball universe. Thankfully, as revealed in Dragon Ball Super, the universe has a way of correcting itself and instead of being ripped apart by the fracture in time and space, a new timeline is simply created and is monitored by the Kai of that universe in the form of a Time Ring. However, while there are no cataclysmic ramifications for fracturing time, it is a very serious offense and Trunks’ time travel mission did not go unnoticed.
In Super Dragon Ball Heroes: Dark Demon Realm Mission! Chapter 1 by Yoshitaka Nagayama, Trunks is finishing up his mission in the past–just as it was originally depicted in the original Dragon Ball storyline–only this time, when Trunks re-entered his time machine and headed back to the future, he was intercepted by a guardian of time named Chronoa and brought to a place outside of time known as the Time Nest. Chronoa confronts him about his meddling with the timestream and accuses him of going back in time and creating his own world–one which didn’t previously exist. Trunks had no knowledge of this strange, barren world but sensed the dark energy emanating from it and vowed to join Chronoa on a mission to find out who was behind this change in the timestream and bring an end to their meddling.
Even though Trunks didn’t create this world that wasn’t supposed to exist, his time-traveling mission brought attention to changes in the timeline and allerted Chronoa of this alteration in history–though Trunks’ heroic efforts go far beyond unwittingly allerting a higher authority to a major threat. It is later discovered that this world was created by evil entities from the Dark Demon Realm who were plotting to cross over into the mortal realm and take control of all of existence. So, to match this threat, Trunks forms a multiversal police force known as the Time Patrol–using his power to defeat the demonic villains and save every conceivable universe in the process.
In the end of this saga, Trunks is able to reach the power level of Super Saiyan God and is instrumental in defeating the Dark Empire Army along with his fellow Time Patrol recruits including Goku, Vegeta, and Gohan. Not only did Trunks bring attention to a change in the timestream by unwittingly fracturing the universe himself, but he also stepped up to eliminate the threat and reached a new level of power in the process–proving that Trunks saved the Dragon Ball universe by accidentally breaking it.