mining theory – Could the threat of centralization be realized if a sufficiently large entity acquired enough Bitcoin?

This is primarily a hypothetical, but not an impossible one.

If a sufficiently large entity such as a massive company with a lot of cash or the U.S. Federal Reserve were to acquire more than half of the available Bitcoin, would it then become a more centralized type of currency given their control? Some alt coins start out like this, with a single entity owning the majority of the coins so that they can maintain centralized control. Bitcoin has always been against that type of centralization, but if one of these entities decided they wanted to gain centralized control, could they do that by taking the action of acquiring a majority of the coins in circulation?

If so what are the ramifications of that? How would we combat that? Is it a real danger or is my hypothetical a little too paranoid?