What to do if cheated by the house contractor?

Last year we entered into a very simple agreement for the construction of our house with the condition that it would be completed within six months. However, there was one very disturbing clause, which wasn't mentioned in the written agreement as contractor removed that point, that if the project gets beyond six months, then per month, Rs 50,000 will be charged. The construction was done quite well for 6 months but things started going pretty bad after my father, rejected a bribe demanded by Junior engineer. Later we got to know that JE, contractor and the person who usually make maps for many people, together they ask for bribe once half construction gets over. As per the earlier agreement total payment is of Rs 63 lakhs 87 thousand. Despite being cooperative and making timely payments towards approximately Rs. 64 lakhs, we found that only around Rs. 45 lakhs was actually used on the construction process. Since June 2024, contactor has not entertained our concerns and gives all sorts of excuses about the delay. He used our money for some other government contracts as he keeps demanding us to make more payments to resume the work. When my father refused further disbursements, he filed a false complaint that we were refusing to pay. Now my house is left under constructed as we did complete payment to him now he refused to work. Also he has many pending payments, like he has not done payment for carpenters, daily wage labors, plumber and mason. So he warned everyone that if they work in our house then he'll not release payment for anyone. Also at the end he's the one whose going to give continuous work to them. He'll make sure to blacklist everyone. So those people are scared now. My father has invested all his retirement amount for this house and now he's the only one who is suffering from this fraudulent contractor. I need help regarding this. What to do? and how to register a consumer complaint online or offline? Please Advice