How should we deal with someone who invokes an unrighteous prayer against us?

A Muslim's supplication against his brother without a reason of injustice and aggression will not be answered, for the Prophet, peace and blessings be upon him, said: "The supplication of a servant continues to be answered as long as he does not pray for a sin or for the severance of kinship ties." The one who supplicates must be advised and shown that what he is doing is an injustice, and enduring the harm of Muslims is better. As for the supplication of the oppressed, it is answered, for the Prophet, peace and blessings be upon him, said: "Beware of the supplication of the oppressed, for there is no barrier between it and Allah." The oppressor must remove his injustice and seek forgiveness from the oppressed.