relentless vs unforgiving

relentless and unforgiving both are adjectives.

Word	Noun	Adjective	Verb	Adverb
relentless	No	Yes	No	No
unforgiving	No	Yes	No	No

As adjectives, relentless and unforgiving are synonyms defined as:

relentless and unforgiving: not to be placated or appeased or moved by entreaty

Other synonyms of relentless include grim, inexorable, stern, unappeasable, unrelenting.

relentless (adjective)	unforgiving (adjective)
never-ceasing	unwilling or unable to forgive or show mercy
not to be placated or appeased or moved by entreaty	not to be placated or appeased or moved by entreaty