Apocolypse Now

Apocalypse now is about an army Colonal called Kurtz, who disappears from the US army, to become a priest-king of a tribe in Cambodia. the film is set in the time of the Vietnam war and Captain Willard (Martin Sheen) is sent on a mission by the US army to go into Cambodia and assassinate Colonal Kurtz as he posses a threat to the US army.
However, when Captain Willard finally captures Colonal Kurtz, he kills him then takes over his reign as King. This film is based on the ideas from the book The Golden Bough, which was written in 1890 by the Scottish anthropologist JG Frazer. The Golden Bough is essetially a vast essay on comparative religion, it traced the roots of Christianity in folklore and of science in magic.
Here is a little clip from the last scene, where Martin Sheen finally kills Kurtz with what is basically the Golden Bough.