Almost every problem in the world would be dealt with meaningfully if we outlawed billionaires.
Everytime I look at small problems or big global problems, if you follow the money trail, it all leads to some billionaire who is either working towards increasing their wealth or protecting their wealth from decreasing.
Everything from politics, climate change, workers rights, democratic government, technology, land rights, human rights can all be rendered down to people fighting another group of people who defend the rights of a billionaire to keep their wealth or to expand their control.
If humanity got rid of or outlawed the notion of any one individual owning far too much money than they could ever possibly spend in a lifetime, we could free up so much wealth and energy to do other things like save ourselves from climate change.
Let’s say you get to pass a law in the USA that would make it illegal to have more than a billion dollars. How would you formulate this law and what would you expect to happen when it’s passed?
You'd probably format it as a percentage of GDP per capita, as it's about limiting wealth disparity (and thus protecting social mobility), distributing wealth growth nationally, and limiting the concentration of financial interest as it's a threat to national and democratic security.
You'd probably want it accompanies by various studies that show that that large wealth disparities are detrimental to social mobility (aka the ability to "work your way up" in classes), and probably some political science papers on the ills of concentrations of wealth.
You'd probably want it to come into force along with laws that limit campaign contributions and big money donors in politics... get rid of that whole "political donations are protected as political speech" crap.... and you'd probably want it as a wealth tax that pays into a sovereign wealth fund with rules on what it can be used for.
There wouldn't be an immediate law to just have a roving gang of enforcers knock down a billionaire's door and send them to jail .... that is just wishful thinking.
Billionaire's would still continue to exist except that anything beyond a certain level of wealth is just taxed either completely or near fully. It would remove the incentive for anyone to own or gain billions of dollars. And it wouldn't occur immediately, it would take years, decades or even lifetimes to make a difference.