Synonyms: implacable
Definition: incapable of being placated
Usage: an implacable enemy
Similar words: inexorable, grim, unrelenting, relentless, unappeasable, unforgiving, stern
Definition: not to be placated or appeased or moved by entreaty
Usage: grim determination; grim necessity; Russia's final hour, it seemed, approached with inexorable certainty; relentless persecution; the stern demands of parenthood
Similar words: unmitigable
Definition: incapable of being mitigated
Usage: stern and unmitigable accusations