What does it mean to be vigilante though? If someone in a position of power, let's say the president of a country, kills someone, it's not vigilante. But if someone who is not in a position of power kills someone, it is? I'm genuinely curious how you distinguish vigilante violence.
I have wrestled with this question for some time for my own philosophy, and I eventually came to the conclusion that there is no distinction other than one of pragmatism, transparency, and maybe, if we're lucky some level of credibility. There is no moral difference between vigilante violence and state-sponsored violence. But there can be a practical distinction based on social organization. If everyone can go around enforcing the law on their own, there is no order to law enforcement and there is a lot of confusion in general.
That distinction only holds up to the extent that the state-sponsored violence is legitimate, transparent, orderly, accountable, etc. The moment it's not, and that moment passes by so often for so many people, it can become oppression, and then vigilante violence can suddenly be morally superior.
This is why it's so critical that governments maintain their legitimacy, follow their own rules, come clean with the public, and make sure to hold themselves accountable. Because it is what holds social government together. It's what makes it worth having.