(Macabre Trope) Forever alive in a horrific state
The Emporer of Mankind (Warhammer 40k): I don't know much about 40k but this is so cool. The Emporer of Mankind has been kept "alive" in a perpetual state of decay via the life support Golden Throne for 10000 years. It is unclear how much of him is biologically, or psychically, "alive".
Hidan (Naruto): His religion grants immortality and while some people say he would die eventually, I like to imagine he is alive living a horrific life buried, hungry, and decaying in that hole.
Nas'hrah (Fear and Hunger): A New God wizard with an attitude, he rejected the constraints of New Godhood and forged his own path. He was reduced to a floating head, but still maintained a significant amount of power in that state. However, once immolated by the traces of Gro'goroth, he became a husk trapped in the ruins of the Dungeon of Fear and Hunger for centuries. He can only communicate telepathically and deflect some magic now, he is literally an equip item now. His attitude and pompousness has not changed in the slightest. In O'saa's ending, iirc he is thrown into a lake.