Ganon

Ganon is Ganondorf's second form, a large blue warthog. Ganondorf changes into Ganon through the use of the Triforce of Power, and also he remains in this form in the Dark World. Ganondorf appears as Ganon in all the Zeldas up to and including The Legend of Zelda: Ocarina of Time, the form also occurs in the Oracle of Seasons and Oracle of Ages' linked ending, The Legend of Zelda: Four Swords Adventures, and is the second phase of the final battle in The Legend of Zelda: Twilight Princess.

Appearances
After Ganondorf broke into the Dark World through the use of a "divine prank", he was changed into Ganon, due to the fact that based on an individual's personality, they are changed into an animal that fits their inner image.

The Legend of Zelda: Ocarina of Time
For the first time, Ganondorf would transform into Ganon, in which a long battle ensued between him an Link. In the end, Zelda held him down and allowed Link to impale his head, and while he was in a pained rage, the Seven Sages opened the void to the Sacred Realm, sealing him there.

The Legend of Zelda: Twilight Princess
Ganondorf was captured and put up for execution by the sages of the Arbiter's Grounds. He survived execution using the power granted him by the goddesses. He killed a sage, and in a hasty response, the others activated the Mirror of Twilight and flung him into the Twilight Realm, where he used Zant to access Hyrule again, though in spirit form.

Taking over Hyrule Castle, Ganondorf was given a mortal body after Zant's magic was delivered to him after his assassination by Midna and a new Link. During the final battle, Ganondorf possessed Zelda by turning into Twilight, and after being purged from her body, reassembled himself into Ganon.

Ganon charged after Link through Twilight portals, appearing randomly and sudden. Link was able to fire arrows into Ganon's head, leaving his stomach succeptable to attack. Eventually, Link morphed into his wolf form and, with the help of Midna, threw him to the side, and attacked his stomach.

Eventually, Ganon's body began to degenerate. Ganon's spirit emerged from the body, and battled Midna equipped with the Fused Shadows. In the end, Ganon emerged victorious, and his spirit was manifested into Ganondorf's body, though he would wind up being defeated.

The Legend of Zelda: The Wind Waker
In the timeline created when Ganon was sent into the Sacred Realm, he somehow escaped imprisonment, and in Ganon form, began to take over Hyrule. Link did not appear. In response, The Gods flooded Hyrule to seal away Ganon and his army.

Over the years, Ganon managed to escape, though he was cut off of his power, therefore he was unable to keep himself in Ganon form and changed into Ganondorf. He eventually was killed by Link.

Oracle games
In the linked ending of the Oracle subseries of Zelda games, it is revealed that the events of the two games were started by Twinrova in an attempt to ressurect Ganon. In the end, they succeeded, though the ritual was incomplete, and Ganon became a mindless beast.

Ganon was powerful due to the fact that he attacked randomly due to no ability to think, though he was sealed way by Link once again.

The Legend of Zelda: A Link to the Past
Ganon sent a portion of his spirit, which was manifested into Agahnim, into Hyrule to break the seal by sending the Maidens, descendants of The Seven Sages, into the Dark World. Link travelled into the Dark World, where he destroyed Agahnim. After the battle with Agahnim, he battled Ganon in the Pyramid of Power, where he was bested by a Silver Arrow. The seal on the Dark World was strengthened.

The Legend of Zelda
Ganon broke free of the Dark World and attacked Hyrule in an attempt into steal the Triforce of Wisdom. He made his base of operations in Death Mountain under Spectacle Rock. Zelda split the Triforce into eight shards, and Link assembled them to fight Ganon, and killed him with the Silver Arrow.

Years later, in Zelda II: The Adventure of Link, Ganon's army made an attempt to revive him by spilling Link's blood onto Ganon's ashes, but failed.

In the Four Swords subseries
Ganondorf sent Dark Link to trick Link into releasing Vaati from the Four Sword in The Legend of Zelda: Four Swords Adventures. While Vaati distracted the Link, split in four by the Four Sword, he searched Hyrule and seized the Dark Trident to become Ganon. At the end of the game, Ganon appears as the final boss as a twist ending, fought in a shrine underneath the Tower of Winds, where he is defeated after Link fires a silver arrow into Zelda's energy bomb, which pierces him. He is sealed away in the Four Sword.