Illegal construction and harassment

I am from south Delhi sarita Vihar and have been facing difficulty in stopping the illegal construction being done by the neighbor on the terrace of the dda flat, the rooms and bathroom constructed is causing a seepage in our flat for which I have given written complaints to the police and MCD both but no action is being taken by either of them. The neighbor from time to time have been damaging our side of the walls by pouring something that is causing the sheds above windows to completely crack & break and the iron rods inside curled. They are of dangerous nature as the neighbor is of malicious nature and once he was arrested for hitting me. He constantly stalk and harass us. Please suggest what can be done so that police and Mcd remove the encroachment and take strict action against the neighbor. Thanks