Hercules

Hercules is one of the primary characters featured in Kingdom Hearts, Kingdom Hearts: Chain of Memories and Kingdom Hearts II. He is a demi-god and son of Zeus, living in Olympus Coliseum. His enemy is Hades, lord of the Underworld. Hercules possesses great strength and can battle the toughest of monsters. He is very supportive of Sora's goal to become a true hero.

Kingdom Hearts
"A legendary hero with godlike strength. He's the son of the gods Zeus and Hera, but not a god himself. The people regard Hercules as a true hero.  He went from "zero to hero" in "Hercules" (1997)

Kingdom Hearts: Chain of Memories
''Son of the gods Zeus and Hera, but not a god himself. With godlike strength and a gentle heart, Hercules is a true hero. He has never lost at the Coliseum games.''

Kingdom Hearts II
''A legendary hero with super strength - and a pretty great fellow, too. Hercules is the son of the gods Zeus and Hera, but he's not a god himself. Not long ago, he joined forces with Sora and his friends to stop Hades from taking over the world.''

''Hercules really impresses the crowds when he battles in the Coliseum. He's never lost a match yet.''

Kingdom Hearts
Hercules is not seen for a while in Olympus Coliseum until he saves Sora, Donald, Goofy and Cloud Strife from Cerberus. Sora, Donald and Goofy run back to battle Cerberus so Hercules can escape with an unconscious Cloud. Upon the defeat of Cerberus, Hercules is impressed with the trio but encourages them to continue training when Phil grants them "Junior Heroes". Hercules later battles Sora in a one-on-one battle in the Hercules Cup.

Kingdom Hearts: Chain of Memories
Hercules' storyline for Chain of Memories is basically the same for as Kingdom Hearts. You meet him where Phil is about to cancel the games because no one else got past his preliminary course. Sora convinces them to keep the games because Sora wants to fight Hercules. Hercules agrees and Cloud shows up to add another contender to the games. During the games, Cloud wants to eliminate Hercules so he can have his lost memories restored. At the end of the course, Cloud and Hercules are fighting to the death and Hades intervenes determined to kill Hercules himself as Cloud could not finish him off. Sora then defends Hercules from Hades. After Hades is beaten, Hercules would like to fight Sora but he is not in his top fighting form and promises Sora to fight him when he is better.

Kingdom Hearts II
Hercules spends most of his days in the coliseum battling Hades' monsters including the Rock Titan and the Hydra. He gets rather tired but hides his exhaustion from Megara and his friends. He later feels depressed for the destruction of the coliseum at the hands of the Hydra. Upon Sora's second visit to the destroyed Coliseum, Hades advises Hercules to regain his pride by fighting Auron in the Underdrome - to the death. Sora, Donald and Goofy stop the fight and help both Auron and Hercules to regain their strength. The group defeat Hades. The credits of the game show Hercules successfully has rebuilt the Coliseum all by himself.

Kingdom Hearts
When fought in the various Coliseum tournaments, Hercules is invincible and protected by a golden aura - Sora must pick up and throw barrels at him to make him vulnerable for a short time. Hercules attacks with various punchs and also slams the ground, unleashing a shockwave.

Kingdom Hearts II
When fought in the Underdrome, Hercules uses powerful punches and headbuts, and can jump and unleash a shockwave when he lands. He can also summon a gold aura, turning himself invincible.

For two fights with Hades, Hercules assists Sora as an ally. He uses his punch attacks, and has two special commands: Aura Guard, which summons a barrier around him to protect Sora, and Aura Sphere, which summons two orbs of energy that, when hit into Hades, render him vulnerable.

Trivia

 * Hercules is the only Protagonist besides Sora, Donald, and Goofy to fight Final Fantasy heroes.
 * Hercules helps you when you fight Hades and Pete in the Underworld as well as fighting with Sora in the Hades Cup in the 2nd visit Olympus Coliseum.
 * You also fight Hercules in the Hercules Cup, Titan Cup and the Paradox Titan Cup.