Controlling shareholder usually means they hold a majority of the shares. Meaning that any shareholder action would require their approval to succeed. basically, every share in the company is one vote on such actions. If he owns 51% of the shares, you’re SOL. If he’s like 48%, and just happens to be the largest block, you might be able to push a shareholder action to oust them- by getting the 52% to vote against him (or the CEO.)

That said, it would partially also depend on any corporate bylaws set up within the corporation, or if said CEO was somehow breaking the law, etc.

Chances are, if you start an effort to do so… you’re going to get fired.

out of curiosity, what’s prompting the question?