Yes, Joseph Stalin is a traitor to his people, because his actions led his people into poverty. Stalin was primarily responsible for the USSR's descent into socialism. With the USSR going socialist, they became impoverished too. Countless people have starved and died under this system. He betrayed his people's best interest and in doing so was a traitor to his country.
You can't say he saved Russia... He brainwashed and controlled the Russians, and was going to do a holocaust towards the Jews before he died.
He didn't rightfully take power either. He took full power after assassinating Lenin and many many other people that the Russian's would have actually considered heroes.