obdurate

obdurate adjective callous, cold, decided, dogged, dogmatic, dogmatical, firm, hard, hardened, hardhearted, harsh, headstrong, immovable, immutable, impervious, impossible to influence, incorrigible, indifferent, indurate, indurated, inexorable, inflexible, insensitive, intractable, intransigent, invariable, iron-hearted, irreclaimable, merciless, mulish, obstinate, opinionated, opinionative, pertinacious, pig-headed, positive, recalcitrant, refractory, relentless, remorseless, resolute, stony, strong-minded, strong-willed, stubborn, tenacious, unalterable, unbending, uncaring, unchangeable, uncompassionate, uncompromising, uncontrollable, unfeeling, unforgiving, unmalleable, unmanageable, unmerciful, unpitying, unrelenting, unresponsive, unstirred, unsusceptible, untouched, unyielding, willful

---

See also: callous, cold-blooded, disobedient, implacable, incorrigible, inexorable, inflexible, insusceptible, intractable, pertinacious, recusant, relentless, remorseless, reprobate, resolute, restive, rigid, ruthless, severe, strict, unaffected, unalterable, unbending, uncompromising, uncontrollable, unrelenting, unyielding, willful