adamant adamantine at a standstill bowelless bulky bullheaded cast-iron certain closed to complaining constant cruel dense disputatious disputing dissentient dissenting dog-eat-dog dour durable enduring fated fateful firm fixed flinty fractious frozen fundamentalist grim hard hard-core hard-line harsh headstrong heartless heavy hidebound immobile immotile immotive immovable immutable impenetrable impersuadable impersuasible impervious implacable impliable impregnable inclement incontestable indefeasible indomitable inductile inelastic ineluctable inescapable inevasible inevitable inexorable inexpugnable inextensible inextensile inextensional inflexible insuperable intractable intractile intransigent invincible inviolable invulnerable iron ironbound ironclad ironfisted ironhanded irreconcilable irremovable irresilient irresistible irrevocable lasting loyal massive merciless mortal mulish muscle-bound necessary noncooperative nonelastic nonstretchable obdurate objecting obstinate obstructive on the barricades orthodox overpowering overwhelming pat pertinacious pigheaded pitiless procrustean proof against protesting purist puristic puritan puritanic rebellious recalcitrant refractory relentless reluctant remorseless renitent repellent resistant resisting resistive resistless retardant retardative rigid rigorist rigoristic rigorous rock-ribbed rockbound rugged ruthless self-willed set settled single-minded solid sot sound stable standpat stationary staunch steadfast steady steely stern stiff stout straightlaced straitlaced strong stubborn sturdy sure sure as death sure as fate tough TRUE unaffected unalterable unamenable unappeasable unassailable unavoidable unbeatable unbending unchangeable uncompassionate uncompassioned uncompliant uncompromising unconquerable uncontrollable uncooperative undeflectable unextendible unextensible unfeeling unflappable unflexible unflinching unforgiving ungiving unimpressionable uninfluenceable unlimber unmalleable unmerciful unmovable unmoved unmoving unpersuadable unpitiful unpitying unpliable unpliant unpreventable unreceptive unrelenting unremorseful unresponsive unshaken unstoppable unsubduable unsubmissive unsuggestible unsurmountable unsusceptible unswayable unswerving unsympathetic unsympathizing untractable up in arms well-built well-constructed well-founded well-grounded well-made without mercy withstanding