He's a mental esper and he already got his hands on manu guides. Even if he cant see them, he can make them kill themself. The lab doesnt know how his ability works so they need to be careful or many guides will die, which means espers will go riot too
Bro is a SSS lv Esper. Have you seen what Gwanyeong's (ML) capable of? He easily broke thru the prison and subdued multiple espers already. And he's capable of doing this without any proper training since his awakening. Now imagine what the doctor can do. We can't bc no one knows his true power. Ppl only knows his intelligence, and there's no way he'd be so fucking cocky without the power to back him up.
Not to mention the guides he has control over. If he manages to kill all 600+ guides, there won't be anyone to guide the espers. And espers going berserk will only lead to more chaos. Plus, it's clear that the body the Doctor is using isn't even his original body. Meaning he somehow possessed or took over another humans body.
So who's to say that the body he's in now isn't even the real deal? What if he just takes over another body in the moment where his "body" is killed? There's too many uncertainties to just kill the doctor on the spot, even with Gwanyeong there.
Basically, the Doctor dtill have many tricks up his sleeves and they can't screw up of 600+people die, and thousand more when beserk
I still don't understand how this old man supposedly has the upper hand when all you have to do is just blow the guy's head off right there. It just makes me feel like everybody is stupid for letting this go on when they could just contained him and not let him near any Guides.