IPA: /ˈkruː.əl.nəs/
KK: /ˈkruːl.nəs/
The quality or state of being unkind or causing pain to others.
The cruelness of his actions shocked everyone in the community.
Cruelness is formed from "cruel" (from Old French *cruel*, meaning harsh or severe) and "-ness" (a suffix meaning the state or quality of). The word "cruelness" refers to the state of being cruel or harsh.
Think of the word 'cruel' which means harsh, and remember that 'cruelness' describes the quality of being harsh.