Many red fash support the states of North Korea, Russia, China, etc.

"Red-fash" isn't a thing, except perhaps for PatSocs and MAGA Communists, like the aforementioned American Communist Party. There are Marxists, and Marxists generally defend AES. There are no Marxists who support Russia except in its anti-NATO stance.

Additionally, this doesn't answer my question. What specifically makes a government authouritarian?

Ofc "real commies" would never support any state.

Are Marx, Engels, and Lenin not "real commies?" I suggest reading The State and Revolution, it's around 25% Marx and Engels quotes and goes over the Marxist Theory of the State. Specifically, the Marxist position is that the State can't be abolished overnight, so we must smash the Capitalist state and replace it with a more democratic worker-state that will itself work out contradictions, transitioning from a policing of people to an administration of things, a state-as-not-a-state.

Most identify as anarchists, nihilists, etc. in order to avoid ideology/terminology that's largely been recuperated by authoritarianism.

Ah, that's why you didn't answer the authoritarian question and reject the Marxist analysis of the State, you're an Anarchist and are trying to claim full ownership of the word "Communism" and reject all of Marxism itself. I suggest reading Marxist theory, not just Goldman and Kropotkin.