Monstro

Monstro is a enormous whale, which terrifies the oceans. One night, when the sea was enraged during a storm, she tried to eat Geppetto and his son, Pinocchio.

Before the Curse
Pinocchio is seen on a raft with his maker and father, the elderly Geppetto, as they brave through the waves of an enraged sea during a stormy night, trying to escape from Monstro, the enormous whale that is chasing after them. Geppetto tells his son that they must abandon ship, and tries to hand him the one life vest they have. Pinocchio tells him to take it, because he is made of wood and therefore can float. Pinocchio then tells him to save himself and dives in the water, just as the whale approaches them. Some time later, Geppetto is seen stranded ashore, recuperating, and he is left brokenhearted by the sight of the lifeless Pinocchio, back to being a mere wooden puppet, face down on the beach. Geppetto takes his marionette in his arms and sobs over the loss of the only son he ever had, until the powerful and benevolent Blue Fairy appears and turns Pinocchio into a real, living boy. ("The Stranger")

Many times later, Pinocchio is seen carving Monstro, in a piece of wood. ("Pilot"/"The Stranger")

Season 1
Twenty eight years later, Pinocchio, now known as August, saw his Monstro's carving, at the office of his father, at Storybrooke. ("The Stranger")