Literally the worst thing I've heard about the Russians was that the east soviet soldiers my grandmother's family had to house were to stupid to get the stove going and instead built an open fire, ruining the kitchen's floor.
Meanwhile, the Americans were busy massacring kindergarteners for being "suspected of being Werwolf" (they'd offer them chocolate for putting on their Hitlerjugend uniforms and singing the NSDAP's hymn, gather a group, then shoot them all according to one of my teachers in school, who claimed to have survived such a massacre by being a few minutes late. I heard comparable stories, though with less detail, from other people all over Germany).
I could go on and on, as I've heard hundreds of tales of such atrocities over the years. Yet somehow, when it comes to the Russians, I've yet to find somebody who witnessed anything (or personally knew somebody who did) rather than learning of it from west-German newspapers after the war.
From what I understand, most of the warcrimes associated with the soviets were committed by the allied partisans (Poles and Czechs, mostly) rather than the regular army, and as they took punitive measurements immediately, these forces were under control by the time they reached Germany. Which would explain why these crimes almost all took place in the eastern colonies (what's Poland and Belarus now).
Also, remember that the soviets were the only allied power that had no interest in destroying Germany, and intended to build Germany into an independent ally (proven, among other things, by their 1951 reunification offer, or the fact that they immediately rearmed the German militias). If they'd really acted like barbarians in Germany, they wouldn't have dared to give Germany any level of power back - like the other allies didn't.