I am NOT denying germans have done a lot of shit. They have killed a lot of people. But they have killed them with Otto-Motor gases and only 1-2 HL used Zyklon B a lot, most others used Zyklon B in small quantities and Motor Gas as a main source.
But all of this is accepted as a fact and nobody denies it. Yet Japan researches were found guilty, 1-2 were death sentenced, some others got a life time sentence but shortly after all of them were free to go and basically got scott free for their most cruel research. They got a stipend from the USA gov in exchange for their research data. No doubt, the KZ-Docs have done some evil things, too but Mengele is one of a very few who was really evil and inhuman.
No doubt, in war all armies are doing crimes. But using cities and villages as B-weapon test ground is something even the Wehrmacht has not done. Among other things. You can do your own research. There is enough data on the net.
Well, america would not talk german. The Marine and Luftwaffe had enough trouble with britain. they could never go to USA. ;)