Construction not completed by builders

I have purchased a flat 4 months back and the construction was almost 85% completed at the time. After registration the builder has stopped taking interest in the project and is not completing the work. Now the concerns from my side are the following: 1. At the time of registration, have signed the sale deed stating the flat has been handed over completed(which was done in good faith that they will be completing it soon). 2. The land was B-khata to begin with and the builder is threatening to go file a complaint against the property for getting the construction done illegally. 3. This was a joint partnership between 4 builders and 2 land owners(where the builders build the flats in the land owners' land and give rights to a certain number of flats to the owner). At some point when the builder stopped doing the constructions, the land owner has taken up some of the tasks pending in the interest of his own( and other buyers) to complete the project(assuming the builder will reimburse him later) and that has kind of resulted in an ego clash between the main builder who was supposed to take care of the constructions and the landowner and is stating this as the reason for not completing the project. Now the land owner is also hesitant to invest further money, seeing that the builder is not cooperating to complete the work now. 4. The builders are a group of 4 and all keep avoiding the responsibility to complete the project. Note: The land owner has ample documents stating the builders have to complete the project by a certain time period, which obviously is past due date now.