You misread some things. For instance, she doesn't [i]have[/i] the ability to use that magic in this, which means she's got... martial arts. Superhuman there, yes, but so are the rest of the combat characters. Who are helpfully not saddled with being only a child in size or having no weapons. There are also explicitly noted ways she can be disabled [i]without[/i] actually killing her and the implicit "if she can't do anything, she's eventually going to stop trying to fight". It doesn't matter too much if you've got unlimited HP when you're not in a position to harm people.

All of which is different from someone that can't even be [i]hampered[/i] by the strongest magic in the setting. If we take the fairly obvious two entries here to throw at him--Nanoha and Mordred--he'd tank Clarent Blood Arthur [i]and[/i] Starlight Breaker despite the fact getting hit directly by either of those is basically game over. First one would also fit the disintegration bill.

[@Crimson Raven] If wikipedia is right, you got his middle names the wrong way round