IPA: //ʌnˈkaɪndɪst//
KK: /ʌnˈkaɪndɪst/
The most unkind; showing the least kindness or compassion.
His unkindest words hurt her feelings deeply.
Comparative: more unkind
Superlative: unkindest
Unkindest → It is formed from "un-" (meaning not) and "kind" (from Old English "cynd", meaning nature or character) and the superlative suffix "-est" (meaning most). The word "unkindest" means not kind in the most extreme degree.
Think of 'not' ('un-') being added to 'kind' to show the most extreme lack of kindness.