Poland spent a good deal of its not-long-past subjugated by either Germany or Russia.
From 1795 to 1918, Poland was split between Prussia, the Habsburg monarchy, and Russia and had no independent existence. In 1795 the third and the last of the three 18th-century partitions of Poland ended the existence of the Polish–Lithuanian Commonwealth.
In 1939, the USSR invades it, with its Nazi buddies. *
Past 1945, Warsaw Pact until 1989.
see also Katyn massacre
Obviously, as others have pointed out, Russian actions since 2007's Estonian cyberwar, the special military operation war in Ukraine and general Russian hankering for the "glory days of the USSR" are only reinforcing this dislike.
*
Hitler rose to power partially on fear and hate for Bolshevism so the world was stunned when Molotov-Ribbentrop Pact was signed in August 1939, a week before Germany invaded Poland. That deal gave eastern half of Poland to the USSR, along with free rein for Russia to screw the Baltics (which Russia did soon afterwards). Stalin might have benefited from reading Mein Kampf as - not before Russia fed the Nazi war machine with raw materials for 2 years - Hitler double-crossed him with his Barbarossa invasion in 1941, bringing us back to the more familiar history we all know (and one considerably more palatable to Herr Putin).
p.s. Besides practical considerations, why did the UK and France not also declare war on the USSR when it attacked Poland? Because their mutual-defense pact with Poland had a secret clause identifying (only) Germany as the power of interest.
p.p.s. Much ink has been spilled on whether a) Stalin was just dumb. Or b) got pre-empted before he could double-cross Hitler himself. One suspects the life expectancy in the 40s-50s of option A historians or documents in Russia might have been limited, so there is no real way to know (the abject failure of Soviet forces in the first weeks of Barbarossa hints at A). One valid-ish concern Russia had in 1939 was a suspicion that the Western powers were just hoping Russia and Germany would start fighting, before swooping in to pick the bones afterwards.
To be fair, while Stalin started out helping Hitler and facilitated WW2, keep in mind 60-70% of German military casualties were sustained on the Eastern Front. The USSR lost 13.7% of its population in that war, compared to UK w 1% and US w 0.3%.