Synonyms for Ill-suited:

adj.

bad (adjective)
inferior, wrong, unfavorable, bad, faulty, poor, unsound, wretched, black, unpleasant, inadequate, unsatisfactory, arrant, invalid, vile, inadvisable, displeasing, detrimental, irremediable, baneful, defective.
inappropriate (adjective)
mismatched, unsuitable.
not suitable (adjective)
inapt, wrong, mismatched, inappropriate, unsuitable, unfit.

n.

inappropriate, unsuited, inapt, ability, unsuitable, unfit.

Other synonyms:

unsuited. inapt. inappropriate, unfit. inadequate
unsuitable.
Other relevant words:
inapt, unsuited, mismatched, inappropriate, unsuitable, unfit.