Despite Future Trunks’ appearances being fairly few and far between, his actions have potentially made a detrimental impact on a timeline he doesn’t even call home, as his most brutal kill may have doomed the entire Dragon Ball universe.
The story of Future Trunks and how he relates to the other Dragon Ball characters is more than a little confusing. This version of Trunks is from a separate timeline, one where Goku dies of a heart virus and Vegeta, along with the rest of the Z Fighters, are killed while battling the Androids. In an effort to save his family and friends while also hoping to make changes to his future, Trunks travels back in time to warn the Z Fighters of the impending Android threat. While his actions in the past have no effect on his future, Trunks inadvertently creates a new timeline upon his trip to the past–splitting the Dragon Ball universe in two. While some of the changes he made to the timeline saved the lives of those closest to him, others may have led to the universe’s total annihilation.
In Dragon Ball chapter 332 by Akira Toriyama, readers are introduced to Future Trunks for the first time–but readers weren’t the only ones. In this chapter, Frieza made his way to Earth following his humiliating defeat by the hands of Goku on Planet Namek. While his battle with Goku left his body mutilated and weak, Frieza made himself strong again by way of cybernetic enhancements. Frieza became Mecha Frieza, a metamorphosis that seemingly made him stronger than he was on Planet Namek–though not strong enough. Since Trunks is only there to warn the Z Fighters about the Androids, he sees Frieza as nothing more than an inconvenient obstacle, and Trunks kills Frieza in an insanely brutal fashion.
Fast-forward to Dragon Ball Super and Frieza has been resurrected by his own people who wanted to bring back the evil emperor so the Frieza Force could return to its former glory. When fans are given a look at Frieza’s form in hell before his resurrection, he is still in his cybernetic state as his appearance in the afterlife was apparently modeled after his most recent appearance when he was alive. When Frieza was resurrected, however, he was given his old body back which he made stronger through training–strong enough, even, to rival the power of a Super Saiyan God. However, Frieza was killed shortly after his resurrection, and upon his return to hell, he was no longer Mecha Frieza as he had been–appearing in his most recent state once more. After some time, Frieza returned to life once again, and this time it stuck. While in his original body, Frieza elevated his power to rival that of a God of Destruction in the form of Black Frieza, and in that form, Frieza took down Goku and Vegeta like it was nothing even when the Saiyans were at their most powerful.
While Mecha Frieza was stronger than the version of him who originally fought Goku, Trunks proved that he wasn’t that much stronger. When Frieza came back to life in his original body, however, he was able to reach an unparalleled level of power. If Trunks never killed Frieza, Frieza never would have gotten his old body back, and if he never did that, he most likely wouldn’t have been able to unlock a form that was stronger than cosmic gods. While it is unclear what Frieza will do with his newfound power, his villainous past indicates that it will be nothing good for the universe, and it seems no one is powerful enough to stop him–proving that Trunks’ most brutal kill may have doomed the entire world of Dragon Ball.