Leninist Communism was always a first cousin of German National Socialism. The latter were small-"s" socialists who added pan-German nationalism and antisemitism to their program to attract the support of the key Army officer class and lesser nobility.
Both are essentially movements of the Left. Fascism OTOH was a rightist phenomenon. Fascists and Nazis understood clearly their important doctrinal differences*, but for wartime political purposes the two were confounded in Western opinion leadership.
* Nazism was about the supremacy of "the people" -- das deutsches Volk -- whereas fascism elevated "the state" to the paramount position. Nazism, like many Left movements, was equalitarian, whereas fascism was not, seeing the old nobility as a valuable authoritarian prop of the state and public order.
They all elevate the state above the individual. I dare say everything else is academic.