@Kat
A: implied to be Saber although I never do confirm that in the story.
Okay then. Most honourable knight who was a total chivalry freak in Zero (to the point of retardation) decided to go ahead and assassinate someone. Yeah I can't see that happening and this makes the death and thus the passing on of the legacy rather contrived at best.
@Gray
A: work specific but the general answer is either cast restriction or characterization fails for the other guys.
A: hatred in the general sense is seen as different from singular focused pure hatred.
A: Too general
A: situationally, as with all heroes.
The first:
So you willingly destroy the characterization of canon characters for the sake of having your OC participate in some fun things good to know.
If the cast is restricted that still doesn't answer why it couldn't have been anyone else in that role.
The second:
Hatred in the general sense encompasses every hate ever. Including that singular vendetta. I could get it maybe if you had it take up the RM slot and had it run like La Pucelle (still not reaching infinite damage) but just a byproduct of hatred of one man against one other man when all of humanities evil pales in comparison.
Q: What about the sword makes it unblockable? It's just a high level hate stick.
The third:
Okay then let's get a little more specific why don't we.
Q: Why Does Satoshi need immunity to all elements if he already has Avalon doing immunity to everything for him?
The fourth:
So he's like Superman except the Nasuverse version and instead of kryptonite and magic it's Fairies and retconning that he's weak to.
Q: What made you decide to transfer such a character archetype to the Nasuverse where it has been demonstrably proven to be damn near impossible throughout at least three characters?
@qwerty
A: depends on the opponent.
Q: He is immortal and immune to everything because Avalon (if he has enough power for dragon fire he has enough power for it's super hax defense mode). So how is it fair fight against anyone other than to aformentioned people?