efficacious Antonyms

inefficacious unrewarding toothless trifling unfruitful unsuccessful useless vain valueless thankless sterile sisyphean senseless resultless purportless profitless pointless motiveless worthless unimportant unremunerative unhelpful uneffective self-defeating unproductive counterproductive counter-productive to no purpose in vain dysfunctional no-win junky unqualified unavailing unprofitable unnecessary irrelevant misspent insubstantial insignificant gainless futile fruitless frivolous feeble feckless fanciful fallow empty doomed