Depends on your lens. Both were violent authoritarians really into hierarchical power. The Nazis stood by that, owned it (Führerprinzip and everything), while the Soviets coated the whole thing with “worker’s rights” paint, keeping the soviets around as mouthpieces of the Nomenklatura. Arguably, owning your shit is better than being shifty about it, so the Nazis were better.
…not to say that Nazis can’t be shifty they constantly are now that you get punched in the face for calling yourself one but the 3rd Reich didn’t hide its ambitions.
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what
Then you can use even more different lens. Number of victims. How they went about it. Whether you were required to send birthday greetings to the leader when you’re in a KZ/Gulag. The list goes on and on and on, if you want to be partisan you could portray things selectively either way, and that’s where you throw up your hands and say “They’re comparable only in so far as they are both incomparably evil”. The Red Khmer killed way fewer people than Nazis or Soviets, yet they’re very much in that “comparable because incomparable” category due to the sheer insanity and ultimately randomness of the policy.
If you’re sitting between the Soviets and the Nazis and saying “Well, I can’t say which is the lesser evil”, you’re no one I would sit at a table with.