Ganon

Ganon is a demonic boar monster who is the King of Evil. Ganon has repeatedly sought the Triforce and threatened balance in Hyrule, sometimes shown transforming from the basic form of the Gerudo Ganondorf, and other times being depicted as Ganon throughout the game.

As a Demon King, Ganon is truly terrible but the focus on darkness means that he is weak to Light Arrows and Silver Arrows.

The Legend of Zelda
Ganon pursues the Triforce, commanding an army of demons.

The Legend of Zelda: A Link to the Past
Ganon plotted his revival from the Dark World. The Seven Sages spoke of a time when he was once a man.

The Legend of Zelda: Ocarina of Time
Ganon is the form Ganondorf assumes when the Triforce of Power takes control over him.

The Legend of Zelda: Oracle of Seasons & Oracle of Ages
Twinrova revived him, since the rite was incomplete, Ganon was mindless and full of rage.

The Legend of Zelda: Four Swords Adventures
Ganondorf steals the Trident and becomes Ganon.

The Legend of Zelda: Twilight Princess
Ganondorf becomes Ganon after obtaining the Triforce.

The Legend of Zelda: A Link Between Worlds
The sorcerer Yuga of Lorule uses the descendants of the Seven Sages to summon and then fuse with Ganon's soul.