Is money taken from the price of a car belonging to a drunken, at-fault driver permissible or forbidden, and is it permissible to waive the right, and what is its reward?

If the intoxicated person was the cause of the accident, then the action taken by the responsible authority, which was to hold him fully accountable and compensate the injured party, is correct. It is permissible to relinquish one's right and forgive the offender, based on the Almighty's saying: "And let them pardon and overlook. Would you not like that Allah should forgive you?" and His saying: "And whoever is patient and forgives – indeed, that is of the matters [requiring] determination." And according to the Prophet, peace and blessings be upon him: "Allah does not increase a servant who pardons except in honor."