Thank you for the additional information.
I'm not sure that I have EVER seen a car financing contract
that did not include the right of the lender to sue the borrower for a post-repossession or post-surrender deficiency. The Uniform Commercial Code
requires that sales of collateral be done in a "commercially reasonable manner", but the auto auctions they use are NOT the place to get the highest and best price.
The longer the financing term, the more likely it is for a finance vehicle to be worth less than the purchase loan. Same for the interest rate, the higher the rate, the more likely the loan today is worth more than the collateral. Depreciating assets like cars should be bought on 3- or 4-year loans, as a matter of financial self-protection in the event that a lender needs to enforce legal rights later.
I'm glad that you realize that if someone is not going to borrow money in the next five years, credit ratings are of little consequence. I've had clients who almost worshiped their credit scores.
There is always the chance of negotiating a surrender of collateral which includes the lender's written waiver of any right to go after the deficiency. That depends on what kind of mood the lender is in. The dollars they could get for the car and the costs of auction also play into their decision (non-legal matters for them, which influence their legal decisions).
The WORST thing someone could do in negotiating turnover, or negotiating a payment plan or reduced interest rate or other modification (which no lender has ANY duty to do at all), is to sign a document called a "confession of judgment". This is often offered to people as "security" for the future payments, usually when that person has no attorney helping them. A confession of judgment is a written grant of permission for the lender to take a judgment against the borrower, with nothing more needed than just filing the breach of contract complain, then skipping EVERYTHING and filing the judgment document. No trial, do not pass "GO", do not collect $200 like in the Monopoly game.