Unsuccessful rhymes with:
successful, successful, successful, successful, stressful, successful, blissful, disgraceful, forceful, graceful, horsfall, houseful, peaceful, purposeful, remorseful, resourceful, stressful, successful, suspenseful, useful
Unsuccessful sounds like:
uncivil, uncouple, unmanageable, unshakable, unshakeable, unsuccessfully, unusable