As the name of the movie indicates, it sends a message- a strong one - that Mercy(Daya) is the most potent weapon. In a very oxymoronic way, the name of the protagonist as well as the antagonist is Daya - Prakash Raj. He has performed his role as meticulously as possible (with his usual gibes). Anybody showing mercy to this character regrets in the film - like Thulasi(Meena)who is a science teacher wanting to transform this brute into a human being-but she is deceived when she almost believes that he has transformed. Lakshmi-Mother is the very embodiment of mercy(head of the institution -Ashram) who can be merciful even to enemies and sinners.Like all stories - this has intriguing flashback where we learn that Lakshmi’s husband Raghuvaran -a Major fails in his duty. He is guilty of childabuse(he rapes an innocent child), Lakshmi, though his wife gives witness in the court against him which earns him seven years of imprisonment. He takes revenge on her using Daya (Prakash Raj). He pretends as a pious person to Mother and when Mother is deceived, she forgives himas he would her own son and he realises the animal in him and his ashamed.
What struck me was the way the power of the mercy was shown. Mercy which becomes intolerable to the person granted. Prakash Raj (Daya) burning his own self(a thought which makes Daya feel l -every burning body is himself) is very moving. He burns it and Cries -but he is very much alive - symbolically it shows his transformation into a new being.