Well, lets look at Bezos, because he has an estimated net worth of 100 billion dollars, but US GDP is something like 18 trillion dollars. And this doesn't even include the world economy. Just what kind of choke-hold is he going to hold on us? Especially needs, because things like water and food are widely decentralized in the US production system.

Also, we're not just talking about this system on it's own. We're talking about private control (Capitalism) vs state control. The history of state rulers blocking off basic needs to political opponents is long and tried, but the history of capitalists doing it is sparse and shallow.

Is there any way to mitigate the possibility of one such as him from simply amassing the largest armed militia in existence and simply taking anything he wants from others by force?

If somebody has the wealth to buy a militia and take everything by force. Then chances are the system has been treating them very very well anyhow, so why would they take everything by force, when they already have it. The way to mitigate this would be to do things like own weapons, which would make endeavors like this massively more expensive.