unreachable vs unreached

unreachable and unreached both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unreachable	No	Yes	No	No
unreached	No	Yes	No	No

As adjectives, unreachable and unreached are synonyms defined as:

Other synonyms of unreachable include out of reach, unapproachable.

unreachable (adjective)	unreached (adjective)
inaccessibly located or situated	inaccessibly located or situated