Kotomine Kirei

Priest Cursed by God
Designated to be a servant of the holy since birth, Kotomine Kirei was born twisted: He could not feel happiness or emotions, and instead craved to see others suffer. For years, Kirei tried to correct himself so he could be normal, but to no avail, even the death of his wife, who deeply loved and understood him, only brought him sadness in the sense that he wasn't able to kill her himself. He wondered if his birth was a mistake, and wondered why he existed without purpose. Now he has turned TFR in a last attempt of salvation, trying to see if the almighty power of wrestling may heal his twisted fate.

Season 2
Still to no avail, his feelings haven't changed, not even his Title Belt gives him any pleasure. He wonders if maybe assassinating a Master in this Holy Grail War he might find the happiness he desperately so desires...

Season 3
Appears in his Fate/Zero self during the Time Merge.

Off-Season 3
When Dan Schneider defeated "Johnny Knoxville" in seconds, Kirei cashed in right then and there, and defeated Dan and won the title."'Yorokobe Shounen, all of this suffering... it brings me great joy.'"

Season 4
He might actually be the one that summoned Johnny Knoxville as his Servant.

Episode 3
Still unable to feel joy, the priest looks for a miracle in the unexpected, and issues a non-title open challenge. Later that night, he would confront a most fierce warrior from a faraway land.

Episode 6
Kojima revealed he summoned Johnny instead, so it is unknown who is his true master, or if he summoned him TO Kirei for some reason.

Episode 8
Kirei went to Hell itself for some reason, and challenged it's twisted master, Mr. Bones. However, he put a condition that he wouldn't resist: If he could challenge his highest ranking avatar, La Parka, he would fight without a Servant. Mr. Bones, perhaps amused by such foolish challenge, accepted. However, probably neither of them actually considered that he could succeed. And that's exactly what he did.

The question that now stands: Why? What's Kirei's plans? Will he perhaps make his way in hell to release All the World's Evils: Angra Mainyu? Or perhaps he will channel it into Johnny?

We just don't know.

Feats

 * On S2E8.5, was the first on the Elimination Chamber and lasted until the end when he fucking won. What a chad.
 * The chad priest does it again, beat V and is on his way to the title
 * Turned an off-season match that OP was forced to do because Janny was unable to play XCOM into a canon match via MITB cash-in, and winning it all just to make OP suffer. Yorokobe Shonen.
 * Might be the one that summoned Johnny Knoxville into this world.
 * Actually Kojima summoned him, but he might still be loyal to Kirei.
 * Actually beat Mr. Bones' avatar / Servant, La Parka holy shit.
 * 'ates Abortion
 * Luvs tofu
 * Simple as