Same word as unacceptable:

below par, damaged, disagreeable, displeasing, distasteful, exceptionable, half-baked, ill-favored, improper, inadmissible, insupportable, lousy, not up to snuff, objectionable, obnoxious, offensive, reject, repugnant, unappealing, undesirable, uninviting, unpleasant, unsatisfactory, unwanted, unwelcome, won't do