- the government can print more money and devaluate your savings (it's like a form of tax one cannot avoid). But it is difficult to "print" more cryptocurrency.
- the government can put limits on amount of money one can withdraw from a bank account. So you legally have the money but cannot use it.
- the bank can refuse to deal with you under AML acts without need to prove anything. But nobody will ban you from mining and exchanging crypto.
- the bank can go bankrupt
The most reliable way to keep your savings safe seems to be to store it as gold. However, there are usually high taxes for buying/selling gold (because why let people store their savings safely) and often governments outright ban gold (folks from US are probably familiar with such situations [1]).