adjective.
Unyielding in severity or strictness; unrelenting.
adjective.
Steady and persistent; unremitting.
The Century Dictionary and Cyclopedia
Incapable of relenting; unmoved by pity; unpitying; insensible to the distress of others; destitute of tenderness.
SynonymsImplacable, etc. See inexorable, and list under unrelenting.
the GNU version of the Collaborative International Dictionary of English
adjective.
Unmoved by appeals for sympathy or forgiveness; insensible to the distresses of others; destitute of tenderness; unrelenting; unyielding; unpitying.