obstinate

Stubbornly adhering to an opinion, purpose, or course, usually with implied unreasonableness; persistent.

From this consideration it is that we have derived the custom, in times of war, to punish […] those who are obstinate to defend a place that by the rules of war is not tenable […]

[…] the junior Osborne was quite as obstinate as the senior: when he wanted a thing, quite as firm in his resolution to get it; and quite as violent when angered, as his father in his most stern moments

Not easily subdued or removed.

1925-29, Mahadev Desai (translator), M.K. Gandhi, The Story of My Experiments with Truth, Part IV, Chapter XXIX, Now it happened that Kasturbai […] had again begun getting haemorrhage, and the malady seemed to be obstinate.

Typical of an obstinate person; fixed and unmoving.

He had the same pile of curly hair, but he was clean-shaven with a heavy, obstinate jowl.