Loan can be defaulted anyway. But according to me risk can be as mentioned below.
1. loan with no collateral 99% risky (depends on amount and rank)
2. Electronics good as a collateral 60% risk as price can be changed more than thinking. So if loan default then there will be no way to cover the amount.
3. Domain as a collateral 50% risk. As domains price can be manipulate.
4. Others accounts as collateral eg: youtube 80% risk. As it can be restored.
5. New listed coin 30% risk. As price can drop too fast.
6. Low volume coin 45% risk. As if price drop there will be no way to sell or will have to sell more lower.
7. ERC20 token collateral. Except number 5 and 6 scammer can send scam by sending other coin. In this case you have to double check price on etherscan and original contact address of the token.
I want to say only altcoin collateral which is listed on multi exchange and volume is good can be risk free.

Edited:
Added number 7.