We should just progressively tax monopolies. Companies will break themselves up to compete, no decade long DOJ case needed.
You may be surprised to learn that the US corporate tax (yes, that one, the main one we already have and everyone pays) was originally introduced in 1909 specifically as an antitrust measure, to clip the wings of US Steel and Standard Oil.
Of course the best laid taxes always get abused or turn into something else entirely.
Yes, this, and we need to have this progressive tax be over the company's total assets, including subsidiaries.