Gollum

Trahald, aka Sméagol or Gollum is a mad Hobbit ruined by the One Ring. He murdered his best friend for it, although he told himself it was his birthday present. When the Ring left him, he chased "that nassssty Bagginses" and his (Bilbo's) first cousin once removed, Frodo to the very Cracks of Doom, where Gollum and Ring fell into the lava.