Eugenics was straight out of Social Darwinism, and Hitler's ideology was partly based on that, or used that to justify his ideology.
NAZIism, in reality, was a religious cult with secret ceremonies and occultic rituals. Unfortunately, that particular aspect is often glossed over in favor of discussing the NAZIs as fascists, but they were significant differences, in say, Franco of Spain and Hitler.
The other fascists do not seem to be involved with the occult as rhe NAZIs were.
Really, in some respects, NAZIism was a revival of paganistic ancestor and race worship.