remorselessly vs unmercifully

remorselessly and unmercifully both are adverbs.

Word	Noun	Adjective	Verb	Adverb
remorselessly	No	No	No	Yes
unmercifully	No	No	No	Yes

As adverbs, remorselessly and unmercifully are synonyms defined as:

Other synonyms of remorselessly include mercilessly, pitilessly.

remorselessly (adverb)	unmercifully (adverb)
without pity; in a merciless manner	without pity; in a merciless manner