Nero Claudius (ruler)

Personally: a version of Nero Claudius who is destined to be forsaken by his people, he has not gone through the toughest moments in his life yet and because of this he is extremely confident and borderlines on cocky
Class: ruler
Hidden abilities: love for the people (he gains double power when near those he considers to be his citizens, he can create a city full of magically created citizens who will fight for him as long as he is considered their ruler)
Instrument of love (when near his "performer" he gains double defense and the power of his grand magic is doubled, when he isn't near his performer he loses access to his grand magic)
Weapons: rose blade, rose spears
Grand magic: the golden theater: star performance
Rank: EX
characteristics: Roman, male, emperor, magician, human
Rank explanation: Nero (ruler) is a far superscript version to his original warrior variant, his hidden abilities are really good and even the draw back on instrument of love isn't that detrimental since his grand magic is only needed in the toughest of fights

King Arthur (alter)

Personality: King Arthur alter is still in the same vein as the other Arthurs, he wants nothing more than to preserve his kingdom however this version revealed in the war he had to wave in that pursuit.
Class: warrior
Weapons: Excalibur Morgan
Hidden abilities: corrupted purity (he has corrupted Excalibur and because of this he takes half damage from casters and deals double damage to rulers and other warrior class opponents)
Block out the sun (he can block out the sun and all the light that it brings, he has night vision, he gains double power at night or in poorly lit areas
Rank: EX
Grand Magic: Excalibur Morgan: siege mode
Characteristics: male, human, british, pseudo-fictional.
Rank explanation: it's an alter version of King Arthur and that's all that I can really say, King Arthur was good because of his sheer strength and not because of any niche or gimmick like a lot of other servants and his alter form falls into that same category

Scathach (alter)

Personality: a version of scathach who decided to use her immortality to take whatever she wanted until she was finally put down by the gods
Weapons: various
Class: warrior
Hidden abilities: warrior training rank: EX (she can summon ethereal soldiers to fight for her, she has the ability to improve the strength stat of any servant just by willing it, she cannot be defeated by an assassin, she is immune to all characteristics based damage that is packaged with a grand magic)
Goddess core (she isn't a divine spirit but she can deal damage to them, she gains pseudo-divinity, she can double the power of her grand magic by sacrificing a human life, she can generate her own mana and doesn't need a master)
Grand magic: this world is mine
Rank: EX+
Characteristics: pseudo-divine, female, Celtic, magician
Rank explanation: scathach has almost no weaknesses, grand Magics can't do all that much damage to her since they will almost always be stuck at a base value, she isn't tied down by her masters limits, can summon warriors to help her, has the potential to do some pretty explosive damage, and even has some support utility, her grand magic is does double damage to human servants and has the potential to deal massive damage.

Julius Caesar (alter)

Personality: Julius Caesar as an alter is pretty violent, he believed the only way to get what he wants is to do it himself, he is very distrustful and tends to fight alone.
Class: warrior
Hidden abilities: solo act
Et tu (alter) (he deals double damage against Roman servants, and when fighting against a group while he is alone he has doubled power)
Weapons: Roman heart (alter)
Grand magic: conquerer of the world (alter)
Rank: B
Characteristics: Roman, alter, male, non-magician,
Emperor
Rank explanation: Caesar is a pretty weak servant over all, warriors are a class that's full of good servants as is so Caesar is rather underwhelming, dealing double damage against romans isn't a very good niche to have so that's his first shortcoming and solo act is underwhelming when compared to other hidden abilities, all of his abilities put him at a disadvantage and his grand magic is a simple buff to his attack power which isn't very helpful when you don't have anything to hit the enemy with.