So what if, Sunny was a police officer who got kicked out of service because of Raghav. He might have been posted somewhere and at that time Raghav might have smuggled in some rare diamonds or something, uske naak ke niche se and he couldn't do anything to catch him, even after knowing Raghav did it.
Raghav told his men to take care of the problem so he never met with Sunny. His men took care of the situation (you don't need me to tell you how) and as a result Sunny was kicked out of the force. He was incriminated and made a scapegoat. Raghav had no idea how his men took care of the situation (and he kind of didn't give a fig about it at that time).
Sunny plots revenge and this helplessness turns him bitter enough to tie Keerti into the situation. Then he might have an unknown connection with Pallavi which we don't know (that Krishna Rao theory everyone is giving).
So Sunny essentially wants to destroy Raghav for destroying his life. It can very well be, he might jump ships if and when Krishna Rao comes into the picture. I know the idea seems far fetched but the kind of connections he has and the way his brain works.. he doesn't seem like an ordinary tattoo artist behind a rich girl.
So, there you go.. my weirdness into the already boiling cauldron of theories. đ