A more realistic concern would be that if you set a 100% wealth tax for all wealth exceeding a million dollars, rich people would just structure their wealth so they don't exceed that cap. In most cases that wealth is primarily in companies (i.e. profiting off other people's labor). So if want to place a ceiling cap on "how much money you can have" (figuratively, let's not pretend this is ever about cash on hand) we'd also need better transparency for corporate ownership.
Personally I think a 100% wealth tax as a "maximum amount of money an individual can have" is a red herring and while wealth taxes are certainly a way to skim some of that surplus value siphoned off by people who own companies (speaking as a company owner myself to be clear), it's just a band aid for the underlying problem.
In my opinion the only logical solution is to abolish individual ownership of companies, effectively requiring all corporations to operate as cooperatives. This isn't an "easy answer" as there are clearly a lot of nuances to what the laws would need to specify in order to make this happen, and it's clearly in stark opposition to how company ownership works in most places today, but it's the only way to fix the problem of excessive wealth accumulation, if we view it as a real problem.
As a reference point, a retirement account funded with $1,000,000, designed to support a $50,000 annual spend (inflation-adjusted), only has a 75% chance of lasting 30 years before the money runs out. (per default parameters on https://cfiresim.com)