unrelenting vs persistent

unrelenting and persistent both are adjectives.

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

As adjectives, unrelenting and persistent are synonyms defined as:

Other synonyms of unrelenting include relentless.

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