May be unique is too strong a word here, but the focus on Nazis is primarily because it scarred the European landscape also. I know other places were impacted as well, not denying it. There were many genocides committed by European powers. The Bengal famine in fact took place during WWII.

What aspects of Nazi ideology were so unique, or even originating in Germany? Racial "purity," "Aryan" supremacy, lebensraum (settler-colonialism), and anti-Semitic "Judeo-Bolshevik" blood libel all came from the western European empires and their colonial Anglo spawn first. Even the fascist corporatism started elsewhere (Italy). At most, the Nazis added a new industrial touch to the genocidal policies first employed against the indigenous peoples of the Americas (and then elsewhere).