What is the optimal course of action with a person who threatens to expose marital infidelity after repentance from it?

The questioner must make a sincere repentance, solely for the sake of Allah, and turn to Allah, supplicating Him to protect her from the evil of this man. She must not succumb to his threats out of fear of her husband or worldly suffering, for the suffering of the Hereafter is more severe, and Allah is more deserving of awe. She should trust that Allah will make a way out for her if she fears Him, and she should utilize all possible means to block this man's path.