insupportable vs unjustifiable

insupportable and unjustifiable both are adjectives.

Word	Noun	Adjective	Verb	Adverb
insupportable	No	Yes	No	No
unjustifiable	No	Yes	No	No

As adjectives, insupportable and unjustifiable are synonyms defined as:

insupportable and unjustifiable: incapable of being justified or explained

Other synonyms of insupportable include indefensible, unwarrantable, unwarranted.

insupportable (adjective)	unjustifiable (adjective)
incapable of being justified or explained	incapable of being justified or explained