Is the prayer of a relative for one's failure answered when he is called "accursed," and what is the expiation for this act?

Cursing a Muslim who does not deserve to be cursed is forbidden, and the Prophet, peace and blessings be upon him, said: "Cursing a believer is like killing him." It is not permissible to curse a specific transgressor (fasiq), even if his transgression is repeated. In Sahih al-Bukhari, it is narrated from Umar that when Abdullah ibn Himar repeatedly drank alcohol, some of the Companions cursed him. The Prophet, peace and blessings be upon him, then said: "Do not curse him, for he loves Allah and His Messenger."

Therefore, the questioner's cursing of his relative is a reprehensible act and an injustice, and the supplication of the oppressed is answered. The remedy for this is sincere repentance and seeking forgiveness from the relative. If this is not achieved, we hope that the sincerity of repentance, abundant seeking of forgiveness, and righteous deeds will suffice.