The final conversation can be respectful without becoming an invitation to restart the argument.

A last conversation has a narrow job. It is there to acknowledge what happened, say what needs saying and close the door kindly, not to establish who was right, which is the work of every previous conversation and was not completed then either. Reopening the case at the end usually just adds one more bad memory to the pile.

Decide beforehand what you want the ending to sound like, and keep to it. Say the true, generous things and leave the rebuttals out. If they raise the old argument, you can decline gently and say you would rather finish well than settle it.