Payment of pending salary.

Hi There. Greetings!! I happen to be a senior IT professional from Bangalore heading with a startup as Head - Enterprise analytics ( Band -I ) and served the organization for eight months, with a specialization in computer science as PhD. The said organization could not process my joining formalities due to COVID -19 outbreak in May-2020 and hence despite of working for one and half month (Ranging from April 2020 to May-2020) and given me a joining as June -2020, upon discussing they agreed to cover the said in upcoming months. The discussion as held between myself and management. The said story continued for eight months and after resignation, organization denied me paying the said May-2020 salary stating to " go ahead and take any action - we will face it " in a merciless manner, what can be resolution over the said atrocity. Despite asking HR and finance, all given diplomatic answer saying they will discuss and come back and denied to speak anything about it. Regards