Inflexible

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