What are the limits of backbiting, and does it include speaking about the faults of one who has wronged the speaker, and what is the authenticity of the hadith: "There is no backbiting for a transgressor"?

Allah has forbidden backbiting to protect the Muslim's honor. One must beware of it and repent if they fall into it. It is permissible to mention a wrongdoer with what he dislikes before a judge to redress an injustice. However, discussing his honor in every gathering is forbidden. The hadith "There is no backbiting for a transgressor" has not been authenticated from the Prophet, peace and blessings of Allah be upon him, but it is attributed to Al-Hasan Al-Basri. Scholars have permitted backbiting concerning a wicked person who openly displays his wickedness, such as publicly known injustice, immorality, and innovations.