unsound vs unfit

unsound and unfit both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unsound	No	Yes	No	No
unfit	No	Yes	Yes	No

As adjectives, unsound and unfit are synonyms defined as:

Other synonyms of unsound include bad.

unsound (adjective)	unfit (adjective)
not sound financially	not in good physical or mental condition; out of condition
not in good condition; damaged or decayed	below the required standards for a purpose
suffering from severe mental illness	physically unsound or diseased
containing or based on a fallacy
physically unsound or diseased
of e.g. advice

unsound (verb)	unfit (verb)
	make unfit or unsuitable