Reverse Dictionary: RELENTLESS

ADJECTIVES
► INEXORABLE unable to be moved or be persuaded to entreaty or request (esp. for mercy); rigidly severe, immovable, relentless → M16
► OBDURATE hardened against persuasion, entreaty, the sentiment of pity, etc.; stubborn, obstinate, unyielding, inflexible, relentless, hard-hearted → 1586
► OBDURATIOUS hardened against persuasion, entreaty, the sentiment of pity, etc.; stubborn, obstinate, unyielding, inflexible, relentless, hard-hearted → 1672 obs.
​► OBDURE hardened against persuasion, entreaty, the sentiment of pity, etc.; stubborn, obstinate, unyielding, inflexible, relentless, hard-hearted → 1624 obs.
► TIGERANTIC of the nature of a tiger; cruel, bloodthirsty, fierce, relentless → a1704 obs.
► TIGERISH ► TIGRISH cruel, bloodthirsty, fierce, relentless → 1573
► TIGERLY tigerish; cruel, bloodthirsty, fierce, relentless → 1633
► TIGEROCIOUS having the qualities of the tiger; cruel, bloodthirsty, fierce, relentless →  1874
► TIGEROUS ► TIGROUS cruel, bloodthirsty, fierce, relentless → 1532 obs.
► TIGERY cruel, bloodthirsty, fierce, relentless → 1859

NOUNS
► OBDURACY stubbornness, obstinacy; obstinate hardness of heart, relentlessness; persistence in evil → 1597
► OBDURATENESS stubbornness, obstinacy; obstinate hardness of heart, relentlessness; persistence in evil → 1618

VERBS
► OBDURATE to harden in wickedness, or against moral influence, etc.; to make stubborn or obstinate; to harden the heart of, to make relentless or pitiless → a1540
► OBDURE to harden in wickedness, or against moral influence, etc.; to make stubborn or obstinate; to harden the  heart of, to make relentless or pitiless → 1598 obs.