
It might have crossed his mind, but I don't think Edmond would've ever considered Q a threat. Q is much weaker than Edmond (especially given the limiter) and as long as Q doesn't have a gun or doesn't have his sunglasses on Edmond could take care of the situation easily.
I really don't think the limiter breaking, or this particular string of events, ever came into Edmond's mind.
Edmond was like... Well, this probably won't be released anyway, so here.
Edmond practically raised Q. Q was all sorts of crazy when he first learned about his powers. At 10 or so he got himself a limiter and there he was able to become levelheaded. He took after his dad and decided to take up sniping. Well s**t happened and around 16 Q befriended Edmond. And since Q had had the limiter in his possession since 10 he didn't know what a Soul Stealer really did or anything.
Q wanted to help kill the Pheonix, and become a monte cristo. So Edmond took Q with him to Dexterity.
It's like... Uh... Well Q learned all his gun stuff from his own family, but Edmond taught him pretty much everything else. Plus Edmond thought that he could use Q to find and kill the Phoenix easier. And what do you know? It worked. He has the Phoenix now.
But Edmond kind of made the mistake of trusting Q's ability to kill the Phoenix curse. The usual way the Monte Cristos do is kidnap the Pheonix, take them to a far away place, then fight them until they consume themselves (through anger or other things). Edmond went on a limb and decided maybe he could stop the soul from reincarnating for good through Q's help. Then he'd be famous and loved forever as a savior (and who doesn't want that?)
Needless to say there was a chance Q'd go crazy but Edmond wasn't expecting it.
Edmond doesn't know much about how souls or the Soul Stealer works. Edmond's never even seen Q use his Rez before. Edmond came by only after Q used his Rez for the whole Aine/Opal thing. And while he knew what happened there he didn't know beforehand, or what to expect afterward. Neither does Q, really.
Soul Stealers are still quite new; only been around for 30 years or so. Knowledge about them is limited, so the whole thing is a learning expierence. Most people didn't even know Q was the Soul Stealer (I'm inclined ot say none of them knew, but that's stupid, there's bound ot be someone). Edmond didn't know when he and Q first met. The conversation only came up later.
Q knows the name for his Rez is The Soul Stealer, and he knows only small things about it (Like, he can take souls. Harhar). He doesn't have much expierence with his own Rez, and, for the most part he is afraid of it, which is why he
started using the Limiter(He obviously uses it for different reasons now). He finds his Rez particularly gruesome due to past events in his life and he hates using it. Even witht he Opal/Aine thing he thinks his Rez is a curse. He never bothered researching it as Limiting his power solved the problem.
And Although Edmond knew Q didn't know about The Prophecies, he made a conscious effort to keep Q away from them in hopes something like this wouldn't happen.
Edmond thought his plan was pretty flawless. I mean, it started out him just using the Soul Stealer but they've been together for so long now they actually do care for eachother, so it's become a lot more complicated.
Right about now Edmond is blaming things on himself. Q likes to keep his power in check, and never use it, so Edmond is probably thinking right about now "If I had told him about The Prophicies, maybe he'd try to stop himself from doing this." Edmond's in a really bad place right now, honestly.
I'd like to say that Q's limiter is like birth control. When he's on it, he's good and neutral and doesn't talk much. When he's off it, his mood changes as the tip of a hat and he's really agressive and spur of the moment. He doesn't think, he just acts on what is instinct. And unfortunately, without the Limiter, his instinct is all his Rez telling him to suck up the Pheonix.
Q still has some hope -- the Limiter is still only
partially broken. So Q's not a complete lost cause yet. He will be if he ever takes his limiter off, or it completely breaks.
But Edmond has never seem him like that, before.
He hasn't even seen Q like this before.
So it really worries him.