Just out of curiosity who are the ones who are mentioned by name in the Talmud that are said to be punished forever?

Yerav’am, Achav, Achitofel, and Geichazi. Individual opinions add some of the following: Avshalom, King Menashe, Achaz, Achazya and all the evil kings of the 10 tribes, the generation of the 40 years in the desert, the followers of Korach and perhaps the entire 10 tribes of that generation when they were exiled.