Defamation and induced resignation

Hi, I was employed with a MNC as a Senior Executive in Karnataka, handling a team of consultants. I was hired as an individual contributor and in the very next year made the regional head of the function I supported. My rating in initial years were neutral. In 2019, my supervisor changed and with that my fortune as well. I was rated a 'Needs improvement - 4' (5 is the lowest) and asked to look out for other roles within the company or move out in 3 months if nothing materializes. My variable pay was withheld and all appeals to the organization to share evidence of poor performance with me were rejected stating due process was followed. It is pertinent to note the following: 1. My offer letter states that 'Target variable pay varies according to our business performance success and your own personal performance. It is payable to you once a year in the month of April subject to you being on the rolls of the organization & not serving notice as on date of disbursement'. My colleagues who were rated '3' or above were paid at least 95% of their variable pay. 2. There were no customer complaints against me during the year nor was I made aware of any deficiency in my performance. There were subjective opinions expressed by a few stakeholders on my personality (argumentative, defensive etc) but none on my performance per se. Even my year end appraisal did not have any adverse remarks against the Objectives / KRAs set in my appraisal. 3. At no point, did my supervisors discuss the feedback or associated plans for improvement with me. If my performance during the year was consistently low, then I should have been placed on a 'Performance Improvement Plan' during the year, as per policy, but this was not done. In fact, my workload continued to be consistently higher than my peers and unsupervised. 4. My supervisor shared my ratings with and delegated a senior member in our team to have the appraisal discussion with me. I was not reporting to this person and sharing subjective opinion and unsubstantiated performance ratings with this person breached my trust, confidentiality and self-esteem. 5. My employment was confirmed upon completion of probation of 6 months. I received increment and variable pay in all years during my employment, except last year. What options do I have? 1. Can I plead my case before Labor Commissioner? 2. Recovery u/s 33(c) of IDA? 3. File summary suit order 37 of Court of civil procedure? (Don't want to throw good money after bad money, by paying 10% court fees) 4. File a criminal cheating police complaint (Withholding my variable pay without evidence of poor performance)?