What is the ruling on saying: "O Allah, deal with him according to Your justice, not Your mercy"?

The supplication against an oppressor by saying: "O Allah, treat them with Your justice" is permissible for the oppressed person. This is because it does not transgress against the oppressor and is not considered an aggression in supplication; rather, it is a permissible form of seeking victory. It is recommended for the oppressed person to supplicate against the oppressor with the equivalent of the injustice inflicted, or less. However, supplicating against a Muslim without cause is not permissible. What is legislated is for a servant to seek forgiveness for their sins and the sins of the believers, and to supplicate for them with mercy.