Unexpectedly high inflation tends to hurt lenders the most. When lenders lend money, it is valuable , but the amount of money that must be returned to him/her is fixed. Over time, the value of the money keeps depreciating and finally when the borrower does return the money, the value decreases to a very small amount, which is not worth much. For example, let's say a borrower borrows money from a lender to buy a car. With time, the value of money depreciated so much that when the borrower finally returns the money, the same amount of money is not even worth buying a box a matches!