A corporation is a legal construct. While it’s theoretically possible for a single business to grow very large, most of the exploitation and legal cover provided by the simple act of incorporation becomes nearly impossible.
Plus without a state to push down competition, it becomes a lot harder to monopolize a market. Ideally there wouldn’t even be a market to monopolize, but that’s a different discussion altogether.
Incorporation is just a formality required by law. Corporations could still exist through internal cooperation without that, as long as there is no outside force that disrupts them.
In the absence of the state, a corporate structure can pursue its own coercive methods to maintain market dominance. And of course, some markets are naturally prone to monopoly due to the barriers to competition.
Anything the state can do, a large enough corporation can do as well. So this logic just doesn’t add up.
What do you think is the quality that would make such an organization still be a “corporation”?
You could argue at some point it wouldn’t be one anymore but what I’m saying is that nothing in this process of gaining power requires a state.
In a functional and lasting anarchist society, there would need to be norms and systems in place to stop this kind of authoritarianism from cropping up.