Englishunchangeable
adjective
many people think of personality characteristics as virtually unchangeable:
unalterable, immutable, invariable, unvarying, invariant, changeless, firm, fixed, hard and fast, cast-iron, set in stone, set, decided, established, permanent, deep-rooted, enduring, abiding, lasting, indestructible, ineradicable, irreversible, unfading, constant, perpetual, eternal, lifelong;
rare incommutable, perdurable.
▷antonyms variable, changeable.
unchangeable Oxford Dictionary of English