Inexorable

1. adjective

   impervious to pleas, persuasion, requests, reason; ; - W.Churchill

   “he is adamant in his refusal to change his mind”

   Similar: adamant, adamantine, intransigent

2. adjective

   not to be placated or appeased or moved by entreaty

   “grim determination”

   Similar: grim, relentless, stern, unappeasable, unforgiving, unrelenting