From my point of view, as a Polish, the worst was FDR. Stalin's puppet who sold half of Europe to commies. No coincidence he was highly respected (we got streets in many cities named after him) and hold up as example how US-USRR relations should look like
As a Finn I understand why Poles now don´t like FDR. The truth was that FDR was naive regarding Stalin:
https://en.wikiquote.org/wiki/Franklin_D._Roosevelt
I just have a hunch that Stalin is not that kind of man. Harry [Hopkins] says he's not and that he doesn't want anything except security for his own country, and I think that if I give him everything I possibly can and ask nothing from him in return, noblesse oblige, he won't try to annex anything and will work with me for a world of democracy and peace.
Response to advice from Ambassador William C. Bullitt to pursue a containment policy against the Soviet Union (1943), quoted in his account in Life (23 August 1948)
We should remember that FDR grossly misjudged Stalin. Stalin did annex the Baltic states, took the eastern part of Poland, around 10% of Finnish territory and Bessarabia from Romania. In addition to that he did puppet many nations in Eastern Europe as well and that includes Poland.