Indeed, the cursers will not be witnesses or intercessors on the Day of Judgment

The Prophet (may Allah's peace and blessings be upon him) informed that whoever frequently and unjustly curses others deserves two punishments: First: He will not be a witness on the Day of Judgment over the nations that the divine messages were conveyed to them through their messengers; his testimony will not be accepted in this world due to his defiant disobedience; and he will not be granted martyrdom, which is dying in the way of Allah.

Second: He will not be able to intercede on the Day of Judgment when the believers intercede for their brothers who have deserved the Hellfire.