Here's what rhymes with unmanageable.

Consider these alternatives

impractical / practical manageable / unmanageable uneconomic / economic superfluous / thus infeasible / feasible unavoidable / avoidable unfeasible / feasible unaccountable / accountable chore / or unviable / double unfathomable / fashionable gargantuan / bantuan illogical / logical nuisance / institutions undignified / side unemployable / employable