nonkindness means synonym of unkindness. Lexicurio rates it Sui generis — a strength score of 88 out of 100.
Etymology
From Middle English nonkendenes (attested as the collective noun for ravens; cf. unkindness); equivalent to non- + kindness.
noun
- Synonym of unkindness.“That this is true needs no words of science to verify, for those who have been through such experience and know the awful sinking of bodily energies which follows lasting grief, not so much the pain of bereavement as of daily harshness, crossing and unkindness—or nonkindness—the mere lack of affection.”