Ingratus est, qui beneficium accepisse se negat, quod accepit: ingratus est, qui dissimulat; ingratus, qui non reddit; ingratissimus omnium, qui oblitus est. He is ungrateful who denies that he has received a kindness which has been bestowed upon him; he is ungrateful who conceals it; he is ungrateful who makes no return for it; most ungrateful of all is he who forgets it. SenecaDe Beneficiis. III. 1.
This was the most unkindest cut of all; For when the noble Cæsar saw him stab, Ingratitude, more strong than traitors arms, Quite vanquishd him; then burst his mighty heart; And, in his mantle muffling, up his face, Even at the base of Pompeys statue, Which all the while ran blood, great Cæsar fell. Julius Cæsar. Act III. Sc. 2. L. 187.