My boss is not accepting my formal resignation and I'm worried about my original certificates

Hello everyone, So, I have a situation at my workplace where I want to resign from my position and I also agreed to serve the notice period which is as per the joining letter. I have not given any kind of contracts although there was one when I first joined a couple of years ago which is now expired and have not renewed by my employer or signed by me. But now when I mailed my resignation letter he says he will not accept. He says many reasons like when I gave you hike last year and you didn't reject it so that means you have virtually renewed your parent contract and etc., Says these are a part of my company policies but not mentioned in offer letter. I tried to go in good terms with my boss as I had no intentions to go against him legally if problems can be solved without it but he insists to continue the mental torture and says that every law will support the company so he don't care even if I go by law against him. He got my original certificates which I'm worried about the most. I'm after constantly putting me under pressure from the day of my resignation, I'm in a state where I'm not mentally prepared to work for him anymore and my mind is very unsettled. I have decided to quit at this moment although I have 1 more month of notice to be served. I'd like to know what are the worst case scenarios I will have to face in case I go legally via labor court or whatever possible way to approach him? I have no idea on the consequences and I'm in desperate need of help. I haven't broken any terms and conditions all these years working under him and I was his most critical resource and always felicitated me for being one of the best employee ever working for him. Now, he behaves very differently, verbally attacking, and creating an image among rest of the employees like I have been unprofessional or unethical towards him. Although I know I have been genuine to my work and it's administration, they are able to creep that fear in me with their aggressive way of talking.