Kirei Kotomine is the major antagonist of most of the routes in the visual novel Fate/stay night, as well as one of the seven participants of the Grail War in Fate/Zero. His entire life, Kotomine had seemingly attempted to capitalize on his possession of magical circuits, which allowed him to practice the rare arts of magecraft. However, Kirei had a remarkable lack of passion in his life, dropping each and every school of magic before reaching mastery, then moving to the next, as if he wasn't satisfied with them. After only mastering self fortification magic, Kirei would go on to be one of the most efficient executors of the church, who still only found a lackluster enjoyment of mercilessly slaughtering mages.
This struggle between an inner depraved mind and his intentions to be a good person would consume him with melancholy for years, until the Fourth Holy Grail War, where he was chosen to be the master of Assassin. While the fourth grail war progressed, Kirei was manipulated by Gilgamesh into embracing his desires to inflict pain on others, and eventually killed his mentor in order to assume control of the Archer-class servant and attempt to gain the grail, despite only expressing interest in assisting the church beforehand. After a brutal confrontation with Kiritsugu Emiya at the end of the war, and suffering from a headfirst dive into the cursed sludge of the grail, he would live on under the guise of his priest persona, waiting until the next grail war in order to wish for the destruction of humanity, and achieve his goal of seeing what his image of true happiness is.
Battle vs. Saruhiko Fushimi (by Dargoo Faust)
WINNER - SARUHIKO FUSHIMI