There is no counterparty risk for the seller in the traditional sense with bitcoin or monero, they're bearer assets, once the transaction is confirmed in your wallet there's no risk for you. You don't need to use violence to make sure you get paid?

What you actually have is the opposite problem (in a sense) - the transaction is irreversible, the seller will receive payment and keep it even if they shouldn't (i.e fraud). So there is more risk for the buyer than in a fiat system where transactions can be reversed by legal processes