unmanageable has 4 distinct synonyms spread across 4 of its 4 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is manageable.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
difficult to use or handle or manage because of size or weight or shape
“we set about towing the unwieldy structure into the shelter”
Synonyms, antonyms and the broader and narrower relations for unmanageable come from Princeton University’s WordNet. Full sources and licences.
incapable of being controlled or managed
“uncontrollable children”