unmerciful vs pitiless

unmerciful and pitiless both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unmerciful	No	Yes	No	No
pitiless	No	Yes	No	No

unmerciful (adjective)	pitiless (adjective)
having or showing no mercy	deficient in humane and kindly feelings
	without mercy or pity