barbarous brutal callous cold-blooded cruel cutthroat ferocious fierce harsh inhuman malevolent merciless rancorous relentless sadistic savage unforgiving unrelenting unyielding vicious vindictive adamant cold dog-eat-dog feral grim hard hard-hearted implacable inexorable ironfisted killer mortal obdurate pitiless remorseless revengeful severe stern stony surly unappeasable unfeeling unmerciful unsympathetic without pity