bullhead

adamant 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 stiff-necked thick-skinned tough unbending uncompassionate uncompromising uncooperative unemotional unfeeling unimpressible unrelenting unshakable unsympathetic unyielding

amenable gentle submissive susceptible yielding