IPA: /ʌnˈkaɪndnəs/
KK: /ʌnˈkaɪndnəs/
The quality of being unkind or not nice to others; a lack of kindness.
Her unkindliness towards her classmates made her very unpopular.
Unkindliness → It is formed from "un-" (meaning not) and "kind" (from Old English "cynd", meaning nature or character) and "-liness" (meaning the state of being). The word "unkindliness" refers to the state of not being kind or lacking kindness.
Think of 'not' ('un-') being added to 'kind' (which relates to nature or character) and then adding '-liness' to describe the state of that nature. This helps you remember that 'unkindliness' means the state of not being kind.