John Locke was a survivor of Oceanic Flight 815 and a previously disabled man who found himself able to walk once he arrived on the Island. He, Rose, and Walt Lloyd were the only people among the survivors that wanted to stay on the Island, believing his special destiny was to protect the miraculous place. In service to this cause, he pushed his friends away, committed murder, and eventually lost his life.
Locke grew up in foster care but, later in life, he met his father, who conned him out of a kidney, ruined his relationship with his girlfriend and finally pushed him out of a window, breaking his back and confining him to a wheelchair. Locke spent the next four years of his life paralyzed from the waist down and looking for his purpose in life. He was then told to attend an Australian Walkabout, after which he found himself aboard Flight 815. On the Island, he served as a friendly, caring mentor, giving Boone a purpose, helping Claire with her pregnancy and child, treating Charlie's addiction, and teaching Walt skills. But his faith and questionable decisions sparked a rivalry with Jack, his philosophical opposite.
When Locke discovered a Hatch on the Island, he was determined to open it, believing his purpose lay inside. He briefly lost faith in the Island while in there, but he left it with his belief renewed, and he set off on a new quest - to join the Island's people. He became their leader, taking the position from Ben Linus, trying meanwhile to protect the Island from new invaders. But once he assumed leadership, the Island began dangerously flashing through time. Locke learned he had to leave the Island and sacrifice his life to retrieve survivors who had left. He tried but thought he failed this mission, and he attempted suicide - only to be stopped and then strangled by Ben. No one attended his funeral.