Considering that there's never actually been a war without rape and pillaging, you're making a pretty bold claim with no evidence.
So there definitely are differences in how the rules of engagement are interpreted from one actor to another. Needless to say this doesn't justify anything the Germans did and I acknowledge that Russia was instrumental in beating the - actual - Nazi's but still, that difference does stand out.
It's a pretty tricky thing because technically the Russians were 'on our side' and the Germans were clearly the enemy and just writing about it in an objective way is hard enough keeping in the back of your mind everything else that the Nazi's were up to.
+ Note that the Germans committed plenty of war crimes in Poland as well and that there were quite a few really bad things that happened in areas under German occupation, but on a relative scale they were considered the 'lesser of two evils' from the point of view of the civilian population that was not directly in the crosshairs of the Germans.
Having no control over your army and the atrocities it commits because the higher ups simply don't care at all about the kind of image they are projecting is exactly the reason why things are utterly out of control in Ukraine today. Lack of discipline, lack of enforcement and in general using the army as a weapon of terror is what is happening, there is zero restraint.
It is not often discussed, but millions of Poles, not just Jews or Jewish Poles were killed in concentration camps.
This (sans "millions" which is my own research finding) was my grandfather's observation as a US officer liberating such camps- there were a lot of non Jewish Poles in such places.
"Lebensraum" came through Polish genocide from what I can tell.
(I am not Polish.)
All 6 siblings of my partner’s grandmother were killed on arrival in Ausschwitz, as were her parents. She was spared by Mengele and subjected to experiments.
Ultimately weighing atrocities against each other is not super productive. But the myth of a “clean Wehrmacht” had been so persistent and convenient that it took decades to root out in German main stream opinion.