Incomplete amenities by builder

I have made flat agreement on Sep2013. Delivery period is 36 months. But builder handed over the flat and sale deed done on Sep2017.But builder could not complete the amenities like Lift, Electrical connection, security room, Electric generator and also handing over of dedicated parking slot. Builder completed only lift and electrical connection on his name in the month of Aug 2018. I have not cleared the balance 10% to be paid by bank to the builder. Now builder has sent letter to clear the balance amount urgently otherwise he will go with legal action. Should I pay the balance amount or should I go legally for completion of balance works. Please advice.