To non-russian speaking users: "Do Svidaniya" means "Goodbye".
To add a bit more, "svidaniye" means a date, and "Do svidaniya" literally means "till [our next] date". In English, "see you" or "see you later" translates closest to the original phrase in Russian.
Often used ironically by movie villains. In English it might almost be taken as a threat.