[@Iatos]
It said limitless in the same sentence that it said that his physical form would explode into gorey bits if he did go limitless mode. So...uh...yeah, he dies when he goes over 9000. Yay.

That being said, that whole thing about 'selecting the headmaster as his opponent in every fight' is probably something that could be done, but he doesn't do that, because Arata wants to have a fun, hard-fought fight. It's a self-inflicted curse for a reason.

Of course, there's people who ignore personality in favor of winning, but I generally try to avoid doing that.

[@GrafRoy Zeppeli]
But if this non-destructive magic is something that effects him or his presence or whatever...why wouldn't he be able to resist it? Still not really understanding what you're getting at here, so clarification might be needed on this subject matter after all. I've never read or watched Trinity Seven, but a quick scan from the wiki showed that the Arata over there can only dispel the magic of those that are magically weaker than him in exchange for being able to dispel literally everything, while Legendary Resistance only works against non-damaging effects, in exchange for allowing him to ignore such effects without having any magical knowledge of his own.

So yeah, could you elaborate on which situations regarding non-destructive magical effects would bypass Legendary Resistance?