persistent vs unrelenting

persistent and unrelenting both are adjectives.

Word	Noun	Adjective	Verb	Adverb
persistent	No	Yes	No	No
unrelenting	No	Yes	No	No

As adjectives, persistent and unrelenting are synonyms defined as:

Other synonyms of persistent include relentless.

persistent (adjective)	unrelenting (adjective)
retained; not shed	never-ceasing
never-ceasing	not to be placated or appeased or moved by entreaty
stubbornly unyielding	punishingly harsh
continually recurring to the mind