efficacious Antonyms

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