Orphan

Orphan is the final boss of Final Fantasy XIII - he is a powerful being that acts as the main power-source for the floating continent of Cocoon - the main villain of the game (Barthandelus) takes the form of Orphan in the climax of the story and fights against the heroes: Orphan's final form is noted as having the highest HP of any boss in Final Fantasy (a title formerly held by Safer-Sephiroth)