Criminal & Civil Defamation Suit for person ridiculing the military

Hi, My father is a retired army officer. Recently in our Community Whatsapp group, one of the members without any direct provocation posted the following statements ridiculing the Military Rank of my Father which he achieved after serving the Indian Army for over 4 decades . My question is:- 1) From the statements mentioned below( We have Whats images of these statements), if we proceed with criminal defamation under relevant sections of IPC, what are the chances of securing a conviction?? 2. What are chances of success in case of a Civil Defamation Case?? Statements Made by the Opposite Party:- "He is a resident not a Col. Army rules dont work in Heritage zone :). What is this ridiculous thing Col Yadav." Thanks