Is it forbidden to curse disbelievers, and what is the ruling on invoking a curse upon them out of anger, even if they have not harmed the one who curses them?

It is impermissible to insult or curse a non-belligerent disbeliever unjustly, and the one who does so commits a sin.

It is also impermissible to specifically curse a named disbeliever, according to the preponderant opinion, whereas cursing disbelievers in general is a right indicated by the Quran.

It is permissible to supplicate against disbelievers in general, but one should not supplicate against a specific disbeliever except with something that does not involve aggression or a religiously forbidden act.