What is the religious view on a son's inability to forgive his deceased father who was cruel, and his inability to pray for mercy for him or recite the Qur'an for him?

Allah Almighty has urged His servants to be patient in the face of harm and to forgive wrongdoers, encouraging this with numerous texts, among them: "And whoever is patient and forgives, indeed, that is of the matters [requiring] firm determination," and "And let them pardon and overlook. Would you not like that Allah should forgive you?" The Prophet, peace and blessings be upon him, forgave the disbelievers after the conquest of Mecca and many of those who had harmed him. Since it is established that forgiveness is generally encouraged, your forgiveness of your father and pardoning him is more deserving than anyone else; due to the immense right he has over you and the obligation to honor him, both alive and dead.