unrelenting

ceaseless constant continual continuous endless implacable incessant inexorable persistent relentless ruthless tenacious unabated unremitting unwavering unyielding

bound bound and determined brick-wall cruel dead set on grim hanging tough hardheaded intransigent iron-fisted mortal perpetual pitiless remorseless rigid set steady stern stiff stiff-necked tough unbending unbroken unflinching unsparing

broken ceasing changeable completed ending finished flexible halting inconstant infrequent intermittent interrupted irregular kind merciful nice occasional stopping surrendering sympathetic terminable varying wavering yielding

compassionate relenting