Can a person who repented atone for the sin of angering his deceased mother?

Disobeying one's parents, especially the mother, is one of the gravest and most severe sins in the sight of Allah, emphasizing her right; for she is the one who bore, nursed, and raised [her child], as stated in the Prophetic Hadith: "Your mother, then your mother, then your mother, then your father." Therefore, a mother's anger due to intentional wrongdoing or negligence on the part of her son is a serious matter that necessitates repentance, seeking forgiveness, performing abundant good deeds, praying for her mercy, fulfilling her will, and maintaining ties with her kin, so that Allah may perhaps accept his repentance.