Ultimatum
Classical Liberal
I'm not familiar with the term, "corporatism".
I absolutely believe the term "corporatocracy" was the word OP was looking for, but I wasn't altogether assured so I couldn't make such an inference. Corporatism is, arguably, less common than that.
But the corporate form of ownership is very useful to capitalism & society.
Oh yes, but that's simply capitalism.
Monopolies are a separate issue, & can be dealt with, eg, breaking up Ma Bell & Std Oil.
Yes, which is why libcaps would fall prey to such an objection raised by the OP, but I was merely pointing out that we aren't all libcaps!