Dragon Ball Super's latest manga chapter takes a look back at Goku's path as a warrior, before finally opening the door to the full mastered Ultra Instinct power. However, in order to reach the milestone of unlocking Ultra Instinct, Goku (as usual) needs an extra emotional push - which he gets from the Galactic Patrolman/angel, Merus. However, what makes an angel forsake divine law in order to protect Earth and its Z-Fighters? The answer is: utmost respect for Goku's spirit as a warrior. It's not just Goku's constantly evolving strength: it's Goku's good-natured attitude about facing the worst monsters in existence.
Warning: Dragon Ball Super Manga 63 SPOILERS Follow!
Merus intervenes in the battle against new villain Moro just in time: Goku and Piccolo are down with near-fatal wounds, and the rest of the Z-Fighters are pretty beat down, and trapped inside an energy dome Moro created. Merus distracts Moro in a fierce battle, while Whis and Beerus warp Goku and Co. to safety, so they can be healed. As soon as he's back on his feet, Goku jumps into the fray to stop Moro, before Merus has to unleash a power that will violate Angelic Laws about acting on the mortal plane. Unfortunately Goku can only do too little, too late; Merus has to power up to full angelic form, in order to seal Moro's new (and unbeatable) ability-copying powers.
While unleashing his final attack against Moro, Merus thinks back to his training of Goku inside the Time Chamber; it was during a break in training that Merus probed Goku about why he's fought so hard to save the universe so many times over. Goku's explanation answers that - and further explains why the Saiyan warrior chooses not to kill (whenever possible):
"It's just, the strongest guys out there tend to be villains, so... If they rise up to do bad stuff again, I just have to become stronger by then, right? I'll fight 'em as many times as it takes, and at some point - just maybe - they'll decide to join the good side. I just think that's way's much more exciting I guess?"
Like so many extraterrestrial and/or divine beings that Goku encounters, Merus is both fascinated and inspired by Goku's philosophical outlook on villains and battle. The unique angel uses Goku's example to motivate his own self-sacrifice, which pushes Goku Ultra Instinct to the mastered level.1comments
Goku's reason for not killing villains is one he's expressed in various ways over the course of the Dragon Ball series. He's repeatedly spared Freeza (except for in Resurrection F), and even when he killed the evil emperor, he eventually brought him back from Hel and restored him to life, for helping to save the universe in the Tournament of Power. The Zen-like rumination on action/consequences is one of Dragon Ball's more understated thematics, but no less of an important one.
Dragon Ball anime is still on hiatus. You can read new manga chapters free online HERE.