inalterable

unalterable

adamant adamantine determined dogged dyed-in-the-wool firm fixed hard hard-and-fast immovable immutable implacable indomitable inexorable intractable invariable iron ironclad obdurate obstinate relentless resolute rigid rigorous set set in one's ways single-minded stand one's ground staunch steadfast steely stiff strict stringent unadaptable unbending unchangeable uncompliant uncompromising unrelenting unswayable unyielding