Putin apologizing for Katyn would be a good start, and also revealing the truth about what really happened in Smolensk with President KaczyĆski's plane.
Interesting website:
Example article:
https://warsawinstitute.org/usa-germany-china-ukrainian-cause/
I am not sure how accurately this site reflects Polish gov’t thinking / analysis (taken as a whole*)?
*Always a dicey endeavor.