INEXORABLE

adamant, adamantine, inexorable, intransigent

(adjective) impervious to pleas, persuasion, requests, reason; “he is adamant in his refusal to change his mind”; “Cynthia was inexorable; she would have none of him”- W.Churchill; “an intransigent conservative opposed to every liberal tendency”

grim, inexorable, relentless, stern, unappeasable, unforgiving, unrelenting

(adjective) not to be placated or appeased or moved by entreaty; “grim determination”; “grim necessity”; “Russia’s final hour, it seemed, approached with inexorable certainty”; “relentless persecution”; “the stern demands of parenthood”

Source: WordNet® 3.1

Etymology

Adjective

inexorable (comparative more inexorable, superlative most inexorable)

Impossible to prevent or stop; inevitable. [from mid 16th c.]

Synonyms: implacable, ineluctable, inescapable, unpreventable, unrelenting, unstoppable, Thesaurus:inevitable

Antonym: exorable

Unable to be persuaded; relentless; unrelenting. [from mid 16th c.]

Antonym: exorable

Adamant; severe.

Antonym: exorable

Source: Wiktionary

In*ex"o*ra*ble, a. Etym: [L. inexorabilis: cf. F. inexorable. See In- not, and Exorable, Adore.]

Definition: Not to be persuaded or moved by entreaty or prayer; firm; determined; unyielding; unchangeable; inflexible; relentless; as, an inexorable prince or tyrant; an inexorable judge. "Inexorable equality of laws." Gibbon. "Death's inexorable doom." Dryden. You are more inhuman, more inexorable, O, ten times more than tigers of Hyrcania. Shak.

Source: Webster’s Unabridged Dictionary 1913 Edition