Ingrate

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late Middle English (as an adjective): from Latin ingratus, from in- ‘not’ + gratus ‘grateful’.

wiktionary

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From Latin ingrātus(“disagreeable”), in-(“not”) +‎ grātus(“pleasing”).

etymonline

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ingrate (n.)

"ungrateful person," 1670s, from earlier adjective meaning "unfriendly," also "ungrateful, unthankful" (14c.), from Latin ingratus "unpleasant, disagreeable," also "ungrateful, unthankful," and "thankless, unprofitable," from in- "not" (see in- (1)) + gratus "pleasing, beloved, dear, agreeable" (from suffixed form of PIE root *gwere- (2) "to favor").