Create a monopoly tax that incentivises large companies to "right size". E.g., if the company is larger than X and has captured a market (like google with search) then tax all revenue above a threshold percentage of the market. For example, the market is $100B and the company makes $90B revenue, then tax away everything above $40B in revenue. This may take away the incentive of a large company to take too much market share and may encourage them to enable competitors. The parameters (company_size, marketshare_percentage, tax rate, etc.) may be adjusted to maximize performance