unrelenting
adjective
not relenting; not yielding or swerving in determination or resolution, as of or from opinions, convictions, ambitions, ideals, etc.; inflexible.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
"Mother is for stiff back-boned unrelentingness in such things," he remarked soberly, after she and Mr. Ewart left the room; "and I 've put my foot into it too," he added dolefully.
From A Cry in the Wilderness by Mary E. (Mary Ella) Waller