heartlessness vs coldheartedness

heartlessness and coldheartedness both are nouns.

Word	Noun	Adjective	Verb	Adverb
heartlessness	Yes	No	No	No
coldheartedness	Yes	No	No	No

As nouns, heartlessness and coldheartedness are synonyms defined as:

heartlessness and coldheartedness: an absence of concern for the welfare of others

Other synonyms of heartlessness include hardheartedness.

heartlessness (noun)	coldheartedness (noun)
an absence of concern for the welfare of others	an absence of concern for the welfare of others