What if employer withheld my relieving letter for 2 years?

I was working as a manager in an NBFC, and the company has withheld my relieving letter for the past two years, causing me mental and physical distress. My current and future employment opportunities are also at risk due to this. Three years ago, an allegation was made against one of my subordinates. After investigation, he resigned and received his relieving letter. No action was taken against other departments involved. I resigned for a better opportunity after eight months of the incident, and my resignation was accepted. However, I have not received my relieving or experience letter to date. Despite repeated emails, there has been no response from HR or any department. I am the sole earning member of my family, and this is affecting my right to earn and support them. Please advise what legal action I can take.