Time and again, Goku has proven himself to be one of, if not the strongest mortal fighters in the universe, and while he always uses his strength for heroic purposes, the seemingly true source of Goku’s power is so much darker than Dragon Ball fans know.
Goku’s strength is derived from the same place as any other Saiyan, though it is true that his base power far exceeds most of the other members of his race. When a Saiyan is faced with their own death or experiences a particularly traumatic event, they can use those raw experiences to channel vast amounts of energy and permanently increase their power levels. One of the first major barriers Goku ever broke in terms of increasing his power is when he was fighting Frieza on Planet Namek and the evil tyrant killed his friend, Krillin, right in front of him. After witnessing Krillin’s death, Goku was able to reach the form of Super Saiyan and ultimately defeat his villainous foe.
In Dragon Ball Super Chapter 40 by Akira Toriyama and Toyotarou, Goku, Android 17, and the rest of the Z Fighters are battling warriors from other universes in the Tournament of Power. In this chapter, 17 seemingly sacrifices himself by self-detonating, creating an explosion he hoped would be enough to defeat an incredibly powerful opponent named Jiren. However, 17’s sacrificial attack barely left a mark on Jiren, though his death inspired Goku to break through another power barrier. At that time, Goku had been working towards mastering Ultra Instinct, an angelic form that makes Goku practically untouchable. Because of 17’s apparent death, Goku was filled with enough raw emotion and newly found focus that he was able to fully channel Ultra Instinct and fight Jiren for real.
Just as Krillin’s death inspired Goku to become a Super Saiyan for the first time, 17’s ‘death’ gave him the push he needed to better harness Ultra Instinct. This is a troubling trend as every major upgrade Goku goes through is inspired by the deaths of one of his friends or allies. While Goku isn’t the one killing them, and they tend to either return to life or reveal they weren’t dead in the first place soon afterwards, it seems like Goku wouldn’t have been able to break those power barriers without first witnessing their deaths, which insinuates that the deaths of those close to him are Goku’s true source of power.
The idea that Goku wouldn’t be as powerful as he is today without the sacrifices of his friends is incredibly dark. One could argue, however, that Goku is honoring their deaths by becoming powerful enough to avenge them. While that is a nice sentiment, it doesn’t take away from the fact that Goku’s major power level increases are only made possible by the deaths of his friends–a disturbing power source Goku taps into that is so much darker than Dragon Ball fans ever imagined.