I don't think this deal is "one sided" against the borrower. He didn't even pay back the principle.
And there are a lot of people who think that ANY level of interest is immoral. We can't just pick a number and claim that all loans should be x apr or less.
The only fair interest rate is the one decided on by the lender and borrower.
The fact that some statists will whine about "one sided deals" just shows their economic ignorance. There will always be those who see exploitation in every transaction. If there is any exploitation here, it is due to the default not the interest rate.
PS Would you see this deal as "one sided" or exploitative, if the lender loaned the money at 0%? Probably not. We'd all say, "Oh how nice of Coconut to help out a friend." Not, "OMG! Coconut is being EXPLOITED! AHHHHH!"
Just shows the inherent bias many of us have against lenders.