This suggetion can be very helpful to all.
I recently got a job and difficult dealing with the co-worker.I had in the past who stab me in the back but have any proof to show he is infact devil. It was too late to prove.

How to deal with the co-worker when they smile infront of you, seems helping a lot but in fact waiting for a time to stab at the back.
Shall we go and tell to the supervisor?
Do the same to them?
Keep quite, I did this in the past was a great mistake infact.

Can I sue the co-worker friend?

Thanx all