authoritarian vs despotic

authoritarian is a noun but despotic is not a noun.

Word	Noun	Adjective	Verb	Adverb
authoritarian	Yes	Yes	No	No
despotic	No	Yes	No	No

As adjectives, authoritarian and despotic are synonyms defined as:

authoritarian and despotic: characteristic of an absolute ruler or absolute rule; having absolute sovereignty

Other synonyms of authoritarian include autocratic, dictatorial, tyrannic, tyrannical.

authoritarian (noun)	despotic (noun)
a person who behaves in a tyrannical manner

authoritarian (adjective)	despotic (adjective)
expecting unquestioning obedience	belonging to or having the characteristics of a despot
characteristic of an absolute ruler or absolute rule; having absolute sovereignty	characteristic of an absolute ruler or absolute rule; having absolute sovereignty
	ruled by or characteristic of a despot