The Holy Grail Wars in Fate/Zero and Fate/Stay Night pairs modern-day mages with famous heroes (known as servants) from history against each other in a battle royale. The winning pair is allowed to make a wish on the Grail to make their deepest desire come true. However, there has never been a clear winner in any of the five instances of The Holy Grail War, due to the fact that it is actually a cover-up for a ritual to reach the "Root:" a record of all knowledge that ever has and ever will exist.
If The Holy Grail War were to have proceeded normally, there are a multitude of master/servant pairings that simply outclass Saber and Shiro, who destroyed the Grail in Fate/Stay Night. Here are the 10 other servant/master duos other than Shiro/Saber who should've Won The Grail War
10 Assassin & Kirei Kotomine
Known as Hassan of the Hundred Faces, Kirei Kotomine's first servant in the Fourth Holy Grail War was gravely underutilized. Hassan is able to divide himself and be in multiple places at once, with each persona having different strengths and weaknesses.
Though weaker than the other servants on this list, Hassan's potential would be maximized by Kirei, since the man is ruthlessly trained in subterfuge. With his strategic genius, Kirei could capitalize on his opponent's weaknesses, potentially assassinating the competition simultaneously when they are at their weakest.
9 Rider & Waver Velvet
A fan-favorite duo in Fate/Zero, the conquerer Iskandar, known more famously as Alexander the Great, was summoned by the mage prodigy Waver. Together, the two were a fearsome team, between Iskander's military prowess and Waver's magics. However, his Noble Phantasm, Ionioi Hetairoi, is one of his greatest strengths.
With it, Iskander displaces his opponent in an alternate reality- a "Reality Marble"- and every ally he has ever fought alongside or commanded through all of history are summoned to reign terror on his foe. With increased mobility due to his Rider class, along with Waver's genius in magic, the two could have completely destroyed the competition.
8 Caster & Sōichirō Kuzuki
Though they did not begin the Fifth Grail War together, Caster and Sōichirō were a pair with a decent shot. Sōichirō was trained as an assassin and in martial arts, who easily outclassed the other mages in the tournament in terms of physical prowess.
Caster-the princess Medea from legend-is a magus who is unmatched by the magical capabilities of any of the mage masters in the Grail War. Bonded through love for one another, the two fought to keep alive. Had they turned their attention towards winning the war, things may have ended differently.
7 Archer & Rin Tohsaka
As the servant EMIYA, Archer is able to trace and copy any weapon he has seen before and use it, which he stores in a Reality Marble. Similar to Gates of Babylon, his Noble Phantasm, Unlimited Blade Works, traps his opponent in this Reality Marble, and unleashes all the weapons he has made onto them.
Along with Rin's prodigal magical talents and a romantic bond that transcends time, Archer and Rin were a formidable team with a ton of potential in Fate/Stay Night. If the two had focused on winning, there would have been little standing in their way.
6 Berserker & Illyasviel von Einzbern
As a homunculus, and a future vessel of The Grail, Illya was very literally destined/designed from birth to win The Holy Grail War. With an unmatched level of mana and magical circuits, Illya has the strongest magical potential of any competitor, and her magical circuits allow her to command Berserker - Hercules - despite his madness enhancement.
Being able to fully control Berserker, who has the ability to return from death, along unmatched magical potential makes the pair the strongest duo in the Fifth Holy Grail War.
5 Saber & Kiritsugu
Though they despised each other in Fate/Zero, together, King Arthur-one of the strongest servants to be summoned-and Kiritsugu-a mage assassin with a spotless record- could have swept the whole tournament.
As an anti-mage, Kiritsugu specializes in killing mages, and without their masters, servants can't make full use of their abilities. Together, they could have mercilessly taken out each competitor by assassinating the master, then double-teaming the now weakened servant. Due to pride, Saber refused to be a part of this tactic, but if she had agreed, there would have been no stopping the pair.
4 Caster & Ryūnosuke Uryū
Caster-the medieval serial killer known as Gilles de Rais-, and Ryūnosuke Uryū-a modern-day serial child killer-were accidentally paired together. Through fate or chance, the two are a match made in hell, as they both share the notion that God must be malicious to allow the two of them to exist to do evil.
The pair actually came quite close to taking out Saber, as Gilles is able to combine the monsters he creates into one gigantic, infinitely regenerating beast of horror. If the two had decided to use Gilles' powers properly instead of just to draw out Saber, they stood a great chance of winning.
3 Lancer & Kirei Kotomine
An extremely strong servant, Lancer, otherwise known as Cú Chulainn, was underused by his master in the Fifth Holy Grail War. With top-tier combat abilities due to his demi-god status and extensive battle training, Lancer was used purely by Kirei to scout the competition.
If the pair truly wanted to win the war, the tournament would not have lasted very long. Lancer's Noble Phantasm, Gaebolg, is a spear strike that will always hit it's target unless they possess a ridiculous amount of luck. With Kirei's penchant for fighting from the shadows along with Lancer's guaranteed kills, the two could have won the tournament before it even got underway.
2 Berserker & Kariya Matou
Let's just state the obvious, Kariya was the weakest mage in the Fourth Holy Grail War, but in order to win, he should have just allowed Berserker -a maddened Lancelot - to do the work.
Lancelot possesses the ability to create a Noble Phantasm out of anything he touches in addition to his mad enhancement, which boosts his already very capable fighting abilities. Oh, he can also steal other servant's Noble Phantasms. That's right, if he touches another servant's Noble Phantasm, he can use it as his own.
1 Archer & Kirei Kotkomine
Gilgamesh, the King of Kings, was a dominant foe in both Fate/Stay Night and Fate/Zero, with his only weakness being his overconfidence. After helping Kirei kill his own master, Gilgamesh became Kirei's new servant. Although the two never fought together, the sheer notion of them in combat is chilling.
Gilgamesh possesses two of the most powerful Noble Phantasms in existence: Gates of Babylon and Enuma Elish/Ea. He is peerless in terms of combat capabilities, and with Kirei's conniving mind focused on victory, there is no chance that they would lose.