Not capable of being persuaded by entreaty; relentless:
Full of or given to revenge.
Not relenting; harsh; pitiless
Difficult to endure; oppressive:
Grim is defined as stern or unmoving.
Not diminishing in intensity, pace, or effort:
Providing a margin for error or shortcomings.
Find another word for unforgiving. In this page you can discover 11 synonyms, antonyms, idiomatic expressions, and related words for unforgiving, like: inexorable, revengeful, unappeasable, avenging, relentless, stern, ruthless, cruel, grim, unrelenting and forgiving.