Illegal Termination

I was working with a company in India registered under factory act, there I used to work as software developer. Since April,2020 after lockdown we need to do WFH and because of this they were not taking attendance. In the month of November, 2020 VPN stopped working and people doing WFH weren't able to connect to office systems. We all(employees doing WFH) complaint several times but in the month of December company terminated me by saying you were absent for continuous 1 month without any approval? IN the month of novemeber I was having email and phone call with HR and my manager. They haven't provided me my November month salary also. They asked me to return the laptop so I informed that I will return after 2 months because of my personal issue. But when I asked regarding full and final settlement they said they can only provide me 1 month salary for the month of november and they won't be providing me any money for my earned holidays. In this company they don't provide any SL or CL, they only provide 15 days paid holiday, if not taken they will pay you that many days salary after the completion of financial year. Now every week they are threatening me that we will destroy your career by filing lawsuite against you for not providing us the laptop and along with this you have violated other company policies as well but in real I haven't done any other violation. The laptop which I am having is general laptop, it doesn't have any data privacy problem, and the cost of laptop is lesser than my salary. They are a very bad company, whenever employee leave them they don't provide them last month salary. What should I don now? I have just started my career, 1.5 years ago and because of lawsuite I am scared.