Gigas Gator is an enemy in Final Fantasy IV: The After Years. It is a more powerful version of the Alligator enemy, but is fought in the same manner. One Blizzara spell is more than enough to dispatch it if the party can't kill it in a simple attack.
Gigas is a popular term for races of giants in fantasy games. Gigas is a Greek word meaning "giant," originally used to describe the race of Gigantes in Greek mythology and is used in the scientific name, as the specific epithet, of hundreds of species of animals and dozens of plant species to denote their size.