tyrannic vs authoritarian

tyrannic is not a noun while authoritarian is a noun.

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

As adjectives, tyrannic and authoritarian are synonyms defined as:

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

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

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

tyrannic (adjective)	authoritarian (adjective)
characteristic of an absolute ruler or absolute rule; having absolute sovereignty	expecting unquestioning obedience
	characteristic of an absolute ruler or absolute rule; having absolute sovereignty