Most Helpful Guy
Probably because he is just wrong in nature as bad as you described him. So he wants to just try another chance to play you out in order to take more advantage of your emotions. Maybe he wants you apologize and feels sorry; which from what i sense according to the weight of your words; that would so unlikely.
When someone is drowned in their darkness and badness; they don't have any concept of "bother" in their mind. I highly doubt he would feel he is bothering anything right now. He most likely sees you as an opportunity. He goes around; get bored; returns and see if he can get involve with the old story again.
Also; there are mistakes in life that can not be unfolded. Sometimes we must just accept the outcome and move on. So even if he has sorriness as motive of his contact; it's meaningless. If he cared enough, he wouldn't put you through any difficult times and force you to leave away with shattered feelings.
Furthermore; the best suggestion i can give is to ignore it. Forget it. Do not overthink about it. Cut as many as contacts you can with him and constantly delete any bridges he tries to build in between you two. Just don't care about it and remain distant. Just move forward for new experiences and try to enjoy life to the fullest without letting his shadow disturb your mind. Completely ignore him. Try to be happier and enjoy your current time. He is not worthy to influence your mind. So just let it go.