firebrand vs instigator

firebrand and instigator both are nouns.

Word	Noun	Adjective	Verb	Adverb
firebrand	Yes	No	No	No
instigator	Yes	No	No	No

As nouns, firebrand and instigator are synonyms defined as:

Other synonyms of firebrand include inciter, instigant, provoker.

firebrand (noun)	instigator (noun)
someone who deliberately foments trouble	a person who initiates a course of action
a piece of wood that has been burned or is burning	someone who deliberately foments trouble