But we dont know,
if what causes the Taint of the Lawbreaker-Power is the same as what gets the Warden to separate your head from the rest of the body.
True. They're almost certainly not, which is why I'm primarily only arguing the Lawbreaker powers, not what the Wardens will punish you for.
By my reading of the books: Intent doesnt matter (at least in some if not most cases).
(example: Healing people from an addiction with mind magic.)
Ah, we're using slightly different definitions of intent here. I'm not talking about motivation or good intentions here, I'm talking about
intending or choosing to do X with magic. For the xample you use, the motivation was to get them off drugs, but there was still the
intent to use Mind Magic. It wasn't an accident.
I'm not arguing he shouldn't get Lawbreaker if he's willing to accept collateral damage in the War with the Red Court (debatably 'good intentions'), I'm arguing that if he
honestly believes his bombs will never kill people (easier said than done), the magic won't be able to change him, since it's what he intends for them to do that shapes his mind and could thus result in Lawbreaker.
I do it this way primarily for setting reasons (it fits Harry's descriptions of why Black Magic is bad), but it also keeps characters from suddenly getting Lawbreaker for killing what they were sure was a vampire...and wasn't (though the Wardens might be unhappy). That can go the other way, of course. If you kill a Red Court Vampire with magic while believing it human I'd rule you get Lawbreaker since the intent was there
But as I was saying, its not clear in the source material.
So every GM needs to think about how it works in his world and stick to it...
True to a large extent, but I still think intent is key, and firmly believe that if you look through the books for Harry's explanations of why Black Magic is evil, they'll back me up that it's vital. I could quote Proven Guilty a bit if people like.