Obdurate

stubborn obstinate unyielding inflexible firm adamant uncompromising dogged immovable relentless rigid harsh hard tough unshakable implacable mulish perverse unbending fixed inexorable hard-nosed uncooperative stiff-necked hard-hearted callous unsympathetic heartless unfeeling mean uncompassionate thick-skinned unemotional yielding bullhead indurate hanging tough tough nut to crack set in stone iron cold fish hard-boiled unimpressible