The greatest check and balance on power over others is the freedom to leave the political union.
It's that simple.
Not that if you fail to act in time it remains as easy as it once was.... quite the reverse.
Nobody can afford not to exercise the right to freedom of association on a regular basis.
Footnote: I suggest the reason it has become as difficult as it now is, is because we have been tempted into relinquishing individual responsibility on the grounds that human nature is evil and depraved and weak.
Meantime the one's selling us that portrayal are the ones who believe they can't learn/improve their abilities. That's what you call Determinism, or Biological Reductionism. This is the position that gives rise to 'scientific' fields like Malthusian Eugenics, Racial Hygiene and Psychiatry.