Is it religiously obligatory for a person to love their father despite his injustice towards them, while still honoring him, showing affection to him, and praying for his forgiveness after his death?

Righteously, one must be dutiful to their father and not mistreat him, no matter what he does. What comes to the heart in terms of lack of love or hatred, which is beyond one's will, is not held against a person. A parent's bad character or shortcomings do not negate his right over his children, for dutifulness and kindness are obligatory even if he were a disbeliever, and disobedience to him is forbidden. Allah Almighty says: (And your Lord has decreed that you shall not worship except Him, and to parents, goodness). And He says: (But if they endeavor to make you associate with Me that of which you have no knowledge, do not obey them, but accompany them in [this] world with appropriate kindness). It was also narrated from the Prophet, peace and blessings be upon him, that Allah will not look at one who is undutiful to his parents on the Day of Judgment, nor will he enter Paradise.