inefficient

Synonyms: can’t hack it careless disorganized extravagant faulty feeble half-baked improficient improvident incapable incompetent ineffective ineffectual inefficacious inept inexpert not cut out for prodigal shooting blanks slack slipshod sloppy slovenly unfit unprepared unqualified unskilled unskillful untrained weak

Antonyms: able capable competent efficient expert useful