Inexorable, a.
Etymology: [L. inexorabilis: cf. F. inexorable. See In- not, and Exorable, Adore.]
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.
Shades of meaning
Fernald has no entry of its own for inexorable; he lists it under severe.
He lists it without comment; the entries above explain its neighbors.