What is the ruling of Islamic law on keeping an apartment that was registered in my name after my aunt's insistence, especially since she accused me of stealing it and filed a lawsuit against me after I refused to return it due to her and her husband's verbal attacks on my honor, my wife, and my mother, knowing that I do not possess the deed to the apartment and the witnesses are only available from my family members?

If the apartment is registered in your name with legitimate ownership, such as through purchase, inheritance, or gift, then it is your property, and no one has the right to claim it unless they present strong evidence as determined by a judge. If it is not your property, then registering it in your name is a mistake for which you must repent. It is not permissible to prevent its owners from accessing it, even if they have wronged you. Their slandering your mother and wife is a lie and a fabrication, which are among the major sins. You must be patient and entrust the matter to Allah, for "no one has been given a gift better or more expansive than patience."