obdurate

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

Antonyms: amenable gentle submissive susceptible yielding