Let's suppose that we institute an income cap and a wealth cap. For the sake of argument, we'll call that 10 million dollars a year, and 100 million dollars. All the existing taxes apply. Nothing gets treated specially: your income for the year will always be capped at 10MM, and your total wealth will be capped at 100MM. It's a 100% tax and knowingly evading it is a crime. If you hit the income limit in two different years, the mayor of your city will award you a plaque, with an optional ceremony, and if you hit the wealth limit, the governor of your state will award you a plaque.

How much pain does that inflict?

None at all.

But nearly everyone harbors some secret hope of becoming a billionaire right now, and the thought of not winning that lottery is enough to make it politically impossible to enact this tiny reform.

And if you can't make reforms, the whole thing may need to be dismantled.

The question you should be asking first is, is it sustainable? If you give someone a bank account with a million in it, they can bring a lot of good to themselves by spending it profligately... but then one day it runs out.

I'm not repudiating (in this thread) capitalism, per se. Only whatever system it is that's abusing OP's protagonist. If you think capitalism inevitably punches someone in the stomach, well, then yeah; you've got your work cut out for you.