Termination and experience letter

I worked in a company for 2 yrs I have offer letter, appraisal letter but soon after the appraisal there was a sudden turn of events I was terminated even thought it was not my fault and one of my colleague was clearly accepted that he was at fault. They suddenly called and threatened me that they take serious actions and all and forcefully got my signature on termination(I think they never wanted termination they just wanted to scare us and wanted to take dominance since it is a startup, but since I got scared and signed the letter they are pinning everything on me ). Without any notice nor previously I had any bad conduct layer they said they can talk on this matter and I no longer wanted to work there so handed my resignation later they said they would need my apology to give my letter and salary later I sent them written letter to issue these, they gave my salary but still told they need apology(accepting all the things they wrongfully had accused me in their termination letter) to give the rel and exp letter