Imagine taking 100% of a rich persons money... making them poor again. That would be a first. (This law will never pass and we know it)
Discussion
The UK had 91% tax from 1945 - 1963
https://www.wolterskluwer.com/en/expert-insights/whole-ball-of-tax-historical-income-tax-rates
Hey, you are talking about European fucking politicians so, if you can expect the most stupid things to happen, you will always be fine...