Now here's a fun one. You know how young children are sometimes determined to show their independence and won't listen? Obstinate is just that.
Obstinate, an adjective, is an attitude that is not willing to yield to instruction, purpose, or a course, no matter what persuasions or arguments have been made. It can also mean something that is not easily remedied or controlled (like an illness).
So, if you have a character that's unwilling to yield to another, Obstinate is a choice word indeed.