Fate/Stay Night's awkward step-brother. Fate/Apocrypha centers around two opposing factions in a Grail War where both sides manage to summon the full assortment of servants and then set them upon each other. Adding in a new class called Ruler and a well-intentioned homunculus, and you have a hero on hero conflict like you've never seen before.
Like with any action anime, there is a dark and often taboo ritual that the fans tend to engage in. A horrible and most unholy chatter among all those who watched the show that leads to an endless loop of he said, she said where no one comes out unscathed. Yes, I mean power levels. A topic of conversation swayed highly by fan opinion and railroaded by particular scenarios that favor one character or another. Many people enter, and no one leaves happy. So now that you know the danger you are in, let's talk about the 10 strongest characters in Fate/Apocrypha.
10 Archer of Red
The famous huntress of Greek Mythology, Atlanta. Skilled with a bow as she is nimble on her feet, Atlante possesses all of the attributes one would expect from the famous Argonaut of myth. Though quick moves and archery are far from her only skills.
Possessing two Noble Phantasms, Atlanta is one to be feared in a Holy Grail War. The first, Pheobus Catastrophe, let's her rain down an overwhelming amount of magical arrows on her foe. The second, Agrius Metamorphosis, sacrifices her humanity to increase all of her base stats. Turning her into a wild animal that is capable of overwhelming even a Ruler class servant.
9 Assassin of Red
Witch, queen, and famous poisoner, Semiramis should never be underestimated. One of the few Servants that can be double summoned, she has the class skills of both the Assassin and Caster classes of the Grail War, despite only being summoned as an Assassin.
Then we have her Hanging Gardens of Babylon. A flying fortress that is able to house a litany of skeletal warriors that she can create. Add to that the fact that it can protect itself by shooting massive laser beams to all who approach, it's no wonder the Red side of that Grail War used it as a base.
8 Lancer of Black
Oh, Vlad, you left us too soon... The vampire, the myth, the legend, Vlad is skilled in shishkabobbing his enemies on large black stakes. The stakes themselves powerful enough to pierce strong armor, only top-class Servants like Karna could even hope to stand a chance against impalement.
Though, let's not forget his other ability. While it is something he would rather not use, Vlad can transform himself into the very epitome of the Dracula legend. He gains all the customary abilities of the famous vampire and can even transform others into his vampiric servants. An ability than can even affect Achilles despite his nearly invulnerable skin.
7 Saber of Red
King Arthur's illegitimate child, Mordred possesses a lot of skills similar to the great King of Camelot. Like her "father," she possesses a powerful blade capable of unleashing a destructive beam and is a quite capable swordsman in every regard. She also shares in her "father's" Mana Burst ability, letting her use mana to increase her power and speed on the battlefield.
Unlike her "father," she is a wild beast in battle. Willing to use whatever it takes to win, she'll punch, bite, and do whatever else to come out on top. Even her swordsmanship is only viewed as a means to an end, Mordred happy to rely on it or discard it entirely in her pursuit of victory.
6 Saber of Black
Another character that left us too soon in the story. Swordsman, Dragonslayer, and all-around great guy, Siegfried is worthy of his epic poem. Encased by the Armor of Fafnir, acquired after bathing in the blood of the dragon he beat in his legend, Siegfried is a great defensive Servant that is basically impervious to all but high-level attacks and Noble Phantasms. Even if they do manage to damage him, the attacks are still degraded by his armor.
Though, defense isn't his only offense. Siegfried if more than a capable swordsman in his own right. Having the sword Balmung lets him take on even an army with ease, and his natural stats as a Servant make other Servants pale in comparison. Truly, he could make almost any servant say "I'm sorry" for daring to challenge him.
5 Rider of Red
Second only to Hercules, Achilles is one of the most celebrated heroes of Greek Myth. Just like his legend, he's impervious to all normal attacks that don't target his heel. Even then, Achilles is a first-rate warrior that can fight near and past death with his Battle Continuation ability. It would take a first-rate Divine Servant or someone that can circumvent his natural hardiness like Vlad to pose a threat.
His only problem is his constant use of mana. The type to quickly run out of juice if he goes too hard too fast, he takes a great master to really shine. Then he can use his great strength, speed, and other abilities to really stand out.
Borrowed strength is still strength. Sieg starts out as nothing more than a young homunculus that was meant to be a mana factory for the Servants of Black but ends up one of the strongest characters in this Grail War. Through a series of complicated circumstances, he ends up acquiring Siegfried's heart and Berserker of Black's, Frankenstein's Monster's, will. This being a very strong combination that lets him use Seigfried's Balmung continuously thanks to Berserker of Black's Galvanism. A skill that lets her recharge her mana faster than other servants.
Did I also mention he becomes a freakin' dragon? After the end of the Grail War, Sieg is able to transform into the dragon Fafnir. The very same dragon Siegfried defeated in his legend. A form that lets him take the Grail to a safe place where no one can abuse its power.
Jeanne is strong, but that's because she's a bit of a cheater. One of the few Ruler class Servants, she is summoned to act as a facilitator in the Grail War. As such, one of her responsibilities is to avoid having things go out of hand. To do this, she is outfitted with servant Command Spells for every servant. Each able to give an almost undeniable command to just about every servant in Fate/Apocrypha. To the point where she can even force them to kill themselves.
She also has abilities that counter most conventional Servants. She has a unique ability to scan past an Assassin's Presence Concealment and most magic doesn't harm her. And if all that fails, she is still able to tell a Servant's name, parameters, and skills with only a look. That's not to say she doesn't have her own unique abilities: Luminosite Eternelle and La Pucelle are some of the strongest defensive and offensive abilities among Servants respectfully.
2 Shirou Kotomine
Masquerading as a mere priest for most of the Grail War, it isn't revealed that he is actually a Servant until partway through the series. The second servant to be under the class of Ruler, he was originally summoned during the 3rd Grail War and was allowed a physical form after coming into contact with the Grail.
70 years later, he joined the Great Holy Grail War of Fate/Apocrypha. The undisputed leader of the Red Servants. He kept his true identity of Amakusa Shirou, the great leader of the Shimabara Rebellion, hidden for a good portion of the war. Instead, acting as a Master to Assassin of Red. It isn't until Vlad becomes Dracula and is subsequentially taken control of by his master, that he reveals his true power. Someone that is strong enough to even counter Ruler's strongest Noble Phantasm, La Pucelle, at the cost of his arm.
1 Lancer of Red
Lancer's of Red's true identity is none other than Karna, one of the distinguished hero of the Mahabharata. True to his epic, Karna is a powerhouse of a servant that is not only the toughest of all of the Servants in Fate/Apocrypha but also among the strongest of all the Servants in the Fateverse.
The Hero of Charity is equipped with a considerable number of skills and Noble Phantasm. With supplementary skills like Discernment of the Poor letting him be a lie detector, armor that is almost impenetrable by both physical or magical means, and a wide array of attacks that can turn the battlefield into a fiery field of pure destructive power. It is only by pure good fortune and plot armor that he is defeated in the Fate/Apocrypha.