Hitler was on the political right and Stalin was on the political left.

However Hitler rose to power originally by PRETENDING to be on the political left.

Authoritarianism is a style, an attitude, an approach to leadership. Fascism is just one expression of it.

His major appeal in Germany was that he was going to stop the socialists and bolsheviks. He was a militarist from the gitgo. He was a populist, but a rightwing populist. If you go to a library that still has old Times and Newsweeks in their stacks, just thumb thru any volume from the early 30s. All coverage will make it clear his appeal was to tradition and strength and racial purity--right wing issues. Saying he was pro-worker wasn't leftist; it was populist.

Hitler promised to break up the aristocrat's land and give it to small farmers but instead he gave the aristocrats positions of power. This was unacceptable to Ernst Rohm who headed up the SA (The Brownshirts). Hitler saw him as a rival and a threat to his power so he had him killed and then replaced the SA with the SS in the famous "Night of the Long Knives".