People pick on Batman because he's a billionaire, but most superheros are pro-cop, pro-establishment, and pro-government. They don't use their abilities for societal change, choosing instead to solve all problems by punching.
Show me a hero arc where the goal is anything but a return to the status quo.
If you pay attention to BatMan(at least some incarnations) It is more about how no one can swoop in and change the entire system not billionaires not vigilantes, but instead you must do some pretty unsavory things to be a “Hero” and it often questions what the difference is between a hero and a villain? If we cross a line to stop a bad guy are we any better than him, and if you notice a lot of the time Wayne Enterprise is just as corrupt and even the villains, Bruce Wayne is no more able to stop the evil than BatMan
k = killers, i = innocents, p = total population, r = killer ratio
p = k+i
r = k/(k+i) = k/p
If an innocent kills a killer: (+1 killer, -1 innocent) from becoming a killer; -1 killer from killing a killer; -1 innocent net change, so r goes up (bad)
Now that you're a killer, any time you kill another killer, it's just -1 killer. r goes down (because the numerator gets smaller faster than the denominator) (good).
This means that the first time you kill someone is always bad, but it gets better if you kill more people. You can offset the net cost of the first kill this way; if r <= 0.5, killing two people will do it. So you're right that if everyone kills one person, the world will be full of killers. But this also suggests that the best course of action is for one person to go around and kill every killer, and then themselves, leaving the world temporarily killer-free!
If I recall, a lot of what Batman has gone through was orchestrated by an Illuminati type group called Court of Owls that controls everything in gotham
That's a problem on how they do businesses rather than the writers. They must go back to the status quo nobody stays dead they need to sell the comics more. There are many characters in Anime that are the power level of western heros but nobody calls them like that. They have a story the story does not go back to status quo. People stay dead cities stay destroyed.