Germany, Russia, Japan and USA all had concentration camps of some sorts and all committed some form of genocide:
- Russia towards the eastern Europe population
- Japan towards the Chinese
- USA it depends if you consider two atomic bombs a genocide, they sure didn't like the Japanese but maybe they are the only ones I would be slightly more hesitant to accuse of genocide
- Germany for sure was the most horrible of them mostly for their sistematic and "effective" approach
- honorable mentions are Italy in Africa (that failed miserably but definitely had the intent) and the United Kingdom in India
Let's be real, at that time most countries where fucking evil. This is not to say that everyone was equally bad (as I said, Germany was really extra bad, and maybe the Nazi degeneracy helped everyone acknowledge how rotten the world was becoming), but if Russia weren't amongst the "winners", their horrors would spoken aloud a lot more.
I rember when "AI" was just the pathfinding in videogames