|Noah Webster's Dictionary|
(a.) Not relenting; unyielding; rigid; hard; stern; cruel.
Unrelenting (2 Occurrences)
Job 6:10 Be it still my consolation, yes, let me exult in pain that doesn't spare, that I have not denied the words of the Holy One. (See NIV)
Isaiah 14:6 He whose rod was on the peoples with an unending wrath, ruling the nations in passion, with an uncontrolled rule. (See RSV)