What is the way to repent from lying to someone who has not forgiven me?

Lying is forbidden, and one must repent from it by feeling remorse, seeking forgiveness, and resolving not to return to it. If the lie has caused harm to a person, then one must seek their forgiveness and strive to convince them to pardon. If they do not forgive, then sincere repentance is sufficient, for Allah Almighty will appease the aggrieved party on the Day of Resurrection. However, if there was no harm, then only repentance and seeking forgiveness are obligatory.