Who’s Building Ethereum’s Next Credit Markets?

It seems that most blockchain-based credit markets are built using over-collateralized loans. Considering debt is one of the largest markets on earth beyond derivatives, I can't help but ask – how can we build non-collateralized debt markets on Ethereum? Are there any current leaders I should be looking out for? How do we hold addresses and users accountable for credit debts? Could credit agencies or banks start working with the Ethereum blockchain? Is it even possible to do this? Looking for any and all insights!