Was there a code in Box 6 of the 1099-C?

If the 1099-C was issued in error -- that is, the debt  had not become legally uncollectible -- then file an amended 2020 return. 

If the payment was made for moral and ethical, not legal reasons, then it probably doesn't require filing a gift tax return.  But if you called IRS and asked three times, you would probably get three different answers.