What do you do in cases where you do not know whether you have committed the sin of legalizing the unlawful or not, knowing that a complete repentance requires informing those to whom you issued a fatwa legalizing the unlawful?

Attributing things to Allah without knowledge is one of the gravest sins, and even more serious is attributing things to Him contrary to His ruling while having knowledge. Part of completing repentance is informing colleagues about the true ruling and admitting the mistake, because repentance includes rectification and clarification so that one does not bear the burdens of those they misled. Shyness before people should not prevent admitting a mistake, and one must speak the truth and not fear the blame of any critic. It is not necessary to tell colleagues that the lie was intentional; rather, it is sufficient to clarify the truth by stating that what was said was a mistake. As for those who have been forgotten, there is no sin concerning them as long as repentance has been completed and clarification has been made to the best of one's ability.