hard-shelled

hard-nosed

callous firm hard as nails hard-line headstrong inflexible obdurate obstinate rough stern strict unbending unfeeling

desperate fierce hard hard-nosed harsh narrow resolute severe stern stiff strict terrible

adamant firm refractory savage

arbitrary callous confirmed cruel drastic exacting ferocious fixed hard-bitten hard-boiled hard-line headstrong immutable inflexible intractable merciless obdurate pugnacious ruffianly ruthless stubborn taut unalterable unbending uncompromising uncontrollable unforgiving unmanageable unyielding vicious violent

amenable easy flexible pliable pliant tolerant uncertain yielding

controllable delicate fragile tender