inflexible

incapable of change; "a man of inflexible purpose"

not making concessions; "took an uncompromising stance in the peace talks"; "uncompromising honesty"

resistant to being bent; "an inflexible iron bar"; "an inflexible knife blade";

incapable of adapting or changing to meet circumstances; "a rigid disciplinarian"; "an inflexible law"; "an unbending will to dominate"