I don’t think the crazy taxes need to be on obscene wealth itself, but on the very lavish and wasteful things people do with that wealth, things that have a very real impact to the rest of society.
For example, private jets or even private chartered flights should have some very steep taxes to offset the cost of all the FAA employees and stuff at all the small airports, all the carbon emissions, and everything.
Yachts, and very large properties also come to mind. Like total square feet of living space of all real estate owned - once it crosses like 10,000 sq ft the annual taxes just get higher and higher. For example 10k-20k sq ft costs $1/sq ft annually, 20k-40k costs $5/sq ft, etc.