What does fascism-communism and authoritarianism have in common?

Fascism is a political philosophy, typically considered far right-wing but with some interesting left-wing elements.

Communism is an economic philosophy that is typically considered far left-wing.

Authoritarianism is a form of government based mainly upon extreme power exercised by the government with limited to no recourse for the people.

Historically, countries that have been Fascist or Communist have wound up having Authoritarian governments.