Lea

Lea is the whole being of Axel. Not much is known about him other than the fact that he lived in the same world as Saïx's whole being, whom he seemed to be close friends with. It is also known that Lea must have had a strong heart in order to produce a humanoid Nobody.

History
At an unknown point in time, Lea's homeworld was taken over by Heartless and he lost his heart in the process along with his friend, Saïx's whole being. Sometime after Organization XIII found his Nobody, who received the name Axel and was inducted into their ranks as Number VIII.

Kingdom Hearts: Chain of Memories
Lea's Nobody, Axel, was among the Organization members stationed at Castle Oblivion, and was charged with weeding out the traitors to the Organization. He engineered most of the games major events, such as freeing Naminè, and was responsible for the deaths of Vexen and Zexion. He was the only member stationed there to survive.

Kingdom Hearts: 358/2 Days
Axel played a large role in 358/2 days, befriending rookies, Roxas and Xion and helping them adapt to life in the Organization. Axel seemed to start the well-known tradition of eating Sea-Salt Ice Cream on the clock tower in Twilight Town, bringing Roxas there on the day he was born and meeting Roxas and later Xion there each day after work, although their friendship ended after Roxas' desertion and Xion's death.

Kingdom Hearts II
Axel was charged with retreiving Roxas and bringing him back to the Organization after Roxas deserted them. He was unsuccessful, however, ad was defeated by Roxas only a few days into the mission. Later, Axel deserted the Organization, himself, and decided to aid Sora and company because Sora held Roxas within him. It soon became clear, though, that Axel's intention to turn Sora into a heartless so that Roxas could be reborn. He soon gave up on this mission, and instead truly helped him in a fight against a mob of Dusks. In a last effort to save Sora, Axel poured all his power in one final attack that destroyed the entire mob, but also drained him of all his life-force. After telling Sora of his wish to see Roxas, Axel used the last of his energy to open a door to the World That Never Was, dying seconds later, ad ending the existence of Lea.