(a.) Unrelenting; firm; determined; unyielding; unchangeable; inflexible; relentless; as, an inexorable prince or tyrant; an inexorable judge\.

adamant adamantine bowelless cast-iron certain cruel dog-eat-dog dogged dour fated fateful firm flinty fundamentalist grim hard hard-core harsh heartless hidebound immobile immovable immutable implacable impliable inclement indefeasible inelastic ineluctable inescapable inevasible inevitable inflexible intransigent iron ironbound ironclad ironhanded irreconcilable irresistible irrevocable merciless muscle-bound necessary obdurate obstinate orthodox pitiless procrustean purist puristic puritan puritanic relentless remorseless resistless resolute rigid rigorist rigoristic rigorous rock-ribbed rockbound ruthless single-minded steely stern stiff straightlaced straitlaced stubborn sure sure as death sure as fate unaffected unalterable unavoidable unbending unchangeable uncompassionate uncompassioned uncompromising uncontrollable undeflectable unfeeling unforgiving ungiving unmerciful unmoved unpitiful unpitying unpreventable unrelenting unremorseful unstoppable unsympathetic unsympathizing unyielding without mercy