Heartlessness is the name for that cruel quality — having no pity — treated as a thing you can talk about. You reach for it when the cruelty itself is the point, not just one person: the heartlessness of the decision. It is a heavy, rather formal noun. Though actually, in conversation people much more often say They were so heartless or That was cruel. Save the noun for when you are naming the quality, as in an essay, a news story, or a careful complaint. It is not usually counted: we do not say a heartlessness the way we say a cruelty in some styles. The meaning is the same harsh one as heartless; the noun just lets you hold the quality still and look at it.

無情、狠心、冷酷