@admitsWrongIfProven

With PoW, past a certain point in the growth of the network, it's prohibitive for most bad actors to spend enough money in hardware and energy to become > 50% of the network and thus gain control.

With PoS, it's exactly the same, just replace “spend enough money in hardware and energy” with “buy enough tokens”.

In any case, if someone/something has the means and the determination to grow past half of the whole network, they will control the consensus and therefore the money.

both PoW and PoS are vulnerable to concentration of power — but both are less vulnerable than centralised systems, eg central banks or credit card companies.