Long lived anarchist societies [1] have traditions and structures that resist this sort of thing. Morality tales, traditions that shame those who aim to put themselves above others, and a tradition of armed self defense serve to prevent subversion from within. These things tend to be frustrated early. If your neighbor gets "picked off" or joins a cult of personality are you going to sit around and wait for it to happen to you or are you going to get your neighbors together and put a stop to it. You're right that individuals cannot stand up to such a threat, that's precisely why they'll form a militia to stop it. Ideally such things can be resolved with words but violence is a perfectly rational response to such a threat.

Centralized power is actually pretty bad at holding ground and subjugating populations. They have to build whole expensive structures of social control to ensure soldiers will fight. As soon as that structure is less convincing than a losing fight they run. The people being subjugated need no such structure. They have every reason to fight to protect themselves, their family, their community, and way of life.

Nothing I've described goes against your definition. A group of people deciding not to feed, house, or allow someone to stay in their midst is not a heirarchy. It's also not government. Just as a group is free to associate it is also free to disassociate.

1. They have long existed and some still persist. The Dawn of Everything by David Graeber and David Wengrow talk about several.