Indirect threat of legal action on me(web site developer) by ex-client via email

In 2017 i was given a freelance project (for which no agreement was signed apart from a non disclosure agreement, and all the communication for project details etc was done via email, telephone calls and watsapp messages). Client company is from Pune and I am from Hyderabad. I cannot post the entire timeline how things happened due to text size limitation here. But the overview is the website ended up with alot of bugs due to complexities involved and other additions requested by the clients. Around 2018 july i we had a heated discussion with the client's 3rd partner and he didnt contact me since, i was in good terms with the client's 1st and 2nd partner and also provided any assistance needed when they gave the development of the website to another developer. yesterday i recieved the below email from the 3rd partner yesterday. It is not explicitly mentioned if legal action will be taken but I need to know what possible actions they can take and how can i prepare myself if the need arises and if i should call to the 3rd partner or even respond to this email. anticipating and would really appreciate your responses. kind regards, Abhishek Email from him: Dear xxxxx, This is with reference to your engagement for the development of our website www.xxxxx.com. While we engaged your services on the basis of your projection of being capable enough to develop the website, at the end of nearly 8 months, we were left with a half baked, non functional product that was of no use to us, nor could have ever been useful given the manner that it lacked basics required in any E-Commerce platform. This has not just resulted in the project being considerably delayed by also in losses due to not being able to transact. While we understand that you put in considerable effort, there was a huge gap in your capability and experience to implement one. We kindly request you to return 50%of the amount paid to you since we did not get what was supposed to be delivered, nor could we continue any further or get any support for the subsequent year as was discussed. Request you to do the needful by the 15th of February, post which we might consider taking action as we deem fit to ensure the right remedy. Warm regards,