determined dogged ferocious fierce harsh implacable inexorable rigorous ruthless single-minded uncompromising unforgiving unrelenting unstoppable unyielding adamant bound bound and determined dead set on go for broke grim hang in hang-tough hard inflexible inhuman mortal obdurate pitiless remorseless rigid stiff stop at nothing strict stringent unappeasable unbending undeviating unflinching vindictive