Is it permissible to supplicate against and curse a specific transgressor, as well as a specific disbeliever, and does this include the use of vulgar language such as "you donkey" and "you dog"?

A Muslim should be chaste of tongue, far removed from reviling and cursing, for "the believer is not a slanderer, nor a curser, nor an obscene speaker, nor an vulgar one." The basic principle in dealing with people is good speech.

A Muslim should not be obscene in speech, even when denouncing or being stern. The Prophet (peace and blessings be upon him) forbade Aisha from using obscene language.

It is forbidden to curse and revile a specific wicked person (fasiq) or to supplicate against him, whether alive or dead. As for a specific disbeliever (kafir) who died upon disbelief, there is no harm in cursing him or supplicating against him. However, if he is alive, it is better not to curse or revile him, as he might repent. It is permissible to supplicate against him for vengeance, defeat, and destruction. If one curses or reviles him, there is latitude in the opinion of those who permitted it if he is a belligerent.

Describing a person as a dog or a donkey is considered reviling and cursing, which is forbidden by Islamic law, and for which one deserves disciplinary action according to the majority of scholars. It is not permissible to liken a Muslim, even if disobedient, to a dog or a donkey.

It is permissible to say "O wicked one" (ya fasiq) to a wicked person if it is for a legitimate purpose, such as giving advice, clarifying his state, or deterring him from his actions, and not with the intention of disparaging him.