Eh. In those parts of europe Soviets/Russians was the evil. First, Soviets/Russians came in 1939. Atrocities started (Katyn, Rainiai, mass deportations to Gulag, pick your favourite). Then Nazis came as a new management and stopped those atrocities just to start their own. Few years later, Soviets rolled back in to resume what they started few years ago.
And then there's another can of worms of how Poland acted to it's neighbours in 1920.
Big portion of that blood is on soviets hands. Both for stabbing Poland and Baltic states in the back. And then running pro-soviet underground resistance that did little to stop nazis but was very successful in triggering well-known nazi response. As well as running their own atrocities on locals that took guns from nazis to defend from pro-soviet resistance.
And then there's another can of worms of how Poland acted to it's neighbours in 1920.