What must I do regarding my many forum posts, which were copied without being read, and may contain curses or polytheistic statements? And is repentance alone sufficient?

Aiding in the spread of forbidden things necessitates repentance. Among the conditions for repentance is striving to remove all traces of the evil. Therefore, whatever corruption has been spread must be erased, people must be convinced of the opposite, and they should be invited to goodness, as an expiation for what has passed, in accordance with the Almighty’s saying: "Indeed, good deeds do away with evil deeds," and the saying of the Prophet, peace and blessings be upon him: "Follow up an evil deed with a good one, and it will erase it."