Who did Jack Sully play in Avatar?

Jack Sully, portrayed by Sam Worthington in the film "Avatar," is a paraplegic former Marine who becomes part of the Avatar Program on the alien planet of Pandora. He operates a genetically engineered Na'vi body, which allows him to interact with the native Na'vi people and navigate their world. Throughout the film, Jack evolves from an outsider to a key figure in the struggle to protect Pandora's environment and its inhabitants.