unmalleable, uncontrollable, unmanageable, balky, refractory, recalcitrant, stubborn, balking, intractible, untractable, more...

tractable, manageable, cooperative, compliant, flexible

insoluble, perplexing, vexing, unwieldy, knotty, thorny, more...

hard to work with,   hard to restrain,   hard to overcome,   hard to fix,   cannot be resolved,   nearly unsolvable,   hard to reason with,   hard to contain,   resolve; insoluble,   hard to treat