useless

adjective
  1. Not fulfilling or not expected to achieve the intended purpose or desired outcome; lacking utility or effectiveness. adjective
    The broken flashlight was useless in the dark.
    He felt useless after failing to fix the leaking faucet.
  2. Having no ability or skill in a particular area or task. adjective
    She was useless at cooking and often burned the simplest dishes.
    Despite his enthusiasm, he was useless at playing the guitar.