I have two thoughts here. First, I'm surprised that you're calling out Eastern Europe specifically. This is one of my favorite videos about Europe:

https://www.youtube.com/watch?v=uJjhNVpSQzw

The entire continent was basically in a constant state of flux (and perpetual wars) through most of its history, ending with WWII in the West, with the fall of the USSR in most of the Central and Eastern Europe, and then continuing with some regional score-settling in the Balkans.

And even this is a bit reductionist: Spain was a dictatorship until about 1975! How crazy is that. This is basically the recent past of the EU.

For the misery of Central and Eastern Europe specifically, "Bloodlands" by Snyder is a good book. And this gets me to my second point: I think you're veering too far into relativism. Yes, every country did some shitty things - that's the history of the world for ya - but the Russian Empire and the German / Austrian / Prussian Empire can be singled out as especially awful when you look at the past 300-500 years. Even just by the simplest metric of the number of people displaced and killed, it's many orders of magnitude worse than what anyone else has done. This distinction is important because the legacy of bloody imperialism continues on the Russian side today - beyond Ukraine - and it's most certainly not excused by the fact that, dunno, Poland occupied Moscow once.