My simplistic solution (I’m a graphic designer, not an economist) for the U.S., is elimination of all corporate income taxes and subsidies, and replacement of the current Internal Revenue Code with an individual flat-tax of around 35% on all income and capital gains above the median per capita income, and a requirement that the highest compensation a corporation pays an individual be limited to a factor of 25-50x the lowest compensation.
These policies would reduce the conglomeration of free markets into oligarchies and provide powerful incentives for those in power to raise the compensation of the bottom tier. They would also maintain the liberty of the markets to maximize productive rebalancing and eliminate reams of taxation regulation and accounting expense. Further, by aligning taxation with the individuals who vote, rather than corporations who buy influence, these policies may increase the ability of the voter to understand taxation, as it would be less obscured by layer upon layer of regulation, loopholes, and corporate obscurity.
I would also tax short-term capital gains at about 50% to increase market stability and rein in the non-productive, market-distorting, effects of speculation and high-frequency trading. Lastly, I would re-separate commercial and investment banks and phase in much tighter limitations on the notional values of derivative hedges.