"Sheer stubbornness" refers to an extreme level of determination and refusal to change one's mind or give up, even when facing difficult or unfavorable situations. Full definition
I'm sure you have many similar, if not worse, experiences with contaminations, misunderstanding and sheer stubbornness of people not getting that a food allergy or intolerance is a serious thing. (theloopywhisk.com)
Evans gives a career - best performance, capturing the moment when Rogers» moral fortitude turns into sheer stubbornness, and RDJ hasn't been this good as Tony Stark since the first Iron Man — this is a darker, more driven Stark than we've ever seen. (laineygossip.com)