How does one say "to hold a grudge against someone" in Latin? A grudge is "a feeling of deep-seated resentment or ill will".
We can resort to Leviticus 19:18. (Do not seek revenge or bear a grudge against anyone among your people,). Both (which occurs much less often than one would think) the Vulgate and Castellio, use the same formula:
nec memor eris injuriae civium tuorum (Vulgate)
neve acceptae ab eis [popularibus] iniuriae memor esto (Castellio)
This is quite interesting choice, for the original text does not mention any "injuiriae" explicitly (nor we can see this in other English translations). This suggestive, I believe, that there is no single word that displays strong-conclusive match for "hold a grudge". At any case, memor acceptae injuriae is classical (saw about 3 occurrences); and there are many instances of accepta iniuria, here is one from Cicero that suggest dolere iniuriā acceptā:
quod mihi non modo irasci gravissima iniuria accepta sed ne dolere quidem impune licet (because I cannot indulge my anger at so deadly an injury or even my bitterness with impunity (Loeb)).