Ashwatthama, a man "sentenced" (actually cursed) to immortality and eternal suffering without love from anybody for his role in the murder of the five sons of the Pandavas and his attempted murder of Arjuna's grandson.
However, in Hinduism, "immortal" does not mean eternal. Even immortal things are dissolved at the end of the universe. The only things that are eternal are the Trimurthi (the Hindu Trinity), Sheshnag (the Eternal Serpent), and the four Vedas. At the end of one universe and the beginning of another, a demon attempted to become eternal by "swallowing" the Vedas as they escaped from Brahma's mouth. This plot was foiled by the god Vishnu.