Jake Sully

Jake takes his dead twin's place in the Avatar program. In a Na'vi body he runs through the forest and Neytiri saves him. Colonel Quaritch promises to fix his legs if he spies on the Omaticaya clan. Jake falls for Neytiri and confesses the truth too late. After the RDA destroys Hometree, he rides the Toruk, gathers the clans and leads the battle. In the end he lives in the Na'vi body for good.

Sixteen years later, Jake is chief of the Omaticaya and father to Neteyam, Lo'ak, Tuk and adopted Kiri, and looks after Spider too. When the RDA returns with a recombinant Quaritch, he runs a guerrilla war and then flees with his family to the Metkayina. He learns to live at sea, but the past catches up. Neteyam dies in the fight, and Jake and Neytiri decide to stay with the reef clan.

Jake and Neytiri mourn their son, and the family travels with Spider. Captured by Quaritch, Jake has to work with him to find the boy. He later surrenders to avoid a massacre, escapes and, along the way, almost kills Spider to protect the secret of his body. He can't do it. He rides the Toruk again, rallies the clans and faces Quaritch in the final battle.

Sam Worthington plays Jake in all three films. In the first he also appears briefly as the dead twin brother, Tom. Per Wikipedia, Cameron picked Worthington after comparing how each candidate read Jake's final speech, including Chris Evans and Channing Tatum.