used vs ill-used

used and ill-used both are adjectives.

Word	Noun	Adjective	Verb	Adverb
used	No	Yes	No	No
ill-used	No	Yes	No	No

As adjectives, used and ill-used are synonyms defined as:

Other synonyms of used include exploited, put-upon, victimised, victimized.

used (adjective)	ill-used (adjective)
employed in accomplishing something	(of persons) taken advantage of
previously used or owned by another
(of persons) taken advantage of