Unmanageable rhymes with:
manageable, manageable, manageable, acknowledgeable, ineligible, manageable, salvageable, acknowledgeable, agregable, changeable, chargeable, corrigible, eligible, exchangeable, illegible, incorrigible, ineligible, intangible, intelligible, interchangeable, knowledgeable, legible, manageable, negligible, rechargeable, salvageable, tangible, unintelligible
Unmanageable sounds like:
uncivil, uncouple, unshakable, unshakeable, unsuccessful, unsuccessfully, unusable