the.com/ungratefulness
The art of receiving a gift and presenting a complaint.
means The failure or refusal to recognize and appreciate kindness, favors, or good fortune given to you.
from Rooted in Latin gratus, meaning pleasing or thankful — pile on the negating un- plus the noun-making -ness, and you get the full, freighted absence of all that grace.
Shakespeare's worstLear called it sharper than a serpent's tooth.
Brain wiringGratitude lights reward circuits; its absence dims them.
Twin wordIngratitude says the same thing, just fancier.