slack-spined

feeble fruitless futile impotent inadequate incompetent indecisive ineffectual inefficient inept limited null powerless unable unproductive unprofitable unsuccessful worthless

abortive anticlimactic barren bootless defeasible emasculate epicene feckless forceless idle inefficacious inferior innocuous inoperative lame neutralized no-go not effective nugatory paltry spineless unavailable unavailing unfruitful vain void withered

able adequate capable competent dexterous effective effectual efficient expert fit fruitful potent powerful productive profitable skillful strong successful sufficient useful valuable worthwhile worthy