Fate/stay night (2006)

Season 1: Episode 21

With the appearance of the mysterious Archer-class Servant, Saber tells Shirou to escape while keeps him occupied. However Shirou, knowning that Saber couldn't defeat him before, foolishly tries to attack him head on and with the snap of his fingers Shirou is quickly defeated. Will Saber have the strength to defeat him, esepecially now knowing his true identity; owner of all the world's treasures, the King of Heroes of ancient Uruk, Gilgamesh.Kirei Kotomine also seems to play a major part in the Holy Grail War and it's not because he's the mediator.