What it the clause in the regard says in the agreement entered between you and the builder?
The builder cannot escape the liability.
You can rope in a qualified engineer from your side, inspect the property and the construction so far completed, get a detailed report of all the drawbacks, including the substandard material used for the construction and the quality of the construction completed so far and the overall assessment.
On the basis of the Engineer's report, you may issue a lawyer's notice to the builder pointing out all the defects and ask for compensation and also completion of the incomplete work, failing which he may dragged to consumer forum seeking relief and compensation.
Dont occupy the villa immediately because the builder may turn the table on you stating that it was you who are the cause for the damages after occupying it hence he will wash away his responsibilities.
Discuss with you lawyer at length before initiating any legal action