I think there’s really only a few solutions to it which all involve some kind of divestiture, it just depends on if you want to target corporations or individuals:
1) a new wave of anti-trust ala Lina Khan and breaking up most major tech companies.
2) passing laws limiting the behavior of, and allowing for the punishment of corporations and group agents as a whole. There’s a lot of philosophical work about how to hold a group accountable for their actions, try searching List and Pettit Group Agency. There’s been a lot of development since then but I’m less aware of it.
3. Caps on decision making power (potentially measured via some weighted stock ownership, or wealth more generally) like suggested above. I agree there would be a lot of second order effects here which are beyond the scope of this comment but I think we’ve clearly gone too far in one direction where single individuals are now essentially funding national party midterms, have increasing power over real world conflicts, and any other of the myriad of corruption issues you can find out in the wild.