Exeter Finance is one of the largest subprime auto lenders in the nation, specializing in high-interest loans to people with histories of not paying bills or defaulting on debt. The company, which has more than 500,000 active loans and a partnership agreement with CarMax, the country’s largest used car retailer, casts itself as a provider of second chances. “We’re here to help,” it says on its website. In reality, though, Exeter’s practices often do the opposite.