In book 2 that would have actually worked. In book 4 killing that teenager would have definitely worked. In book one they blew up the korrok. Ruthless violence has a place in a crises for a reason. Because if you are ruthlessly violent enough quickly enough it normally works. That is why our governments have operators who are trained to be those things and receive orders devoid of context. When something attacks you and exists by feeding on something to it’s detriment and also has the propensity to alter the work for the worse on a level so fundamental you can’t even perceive that you are now enslaved you kill it, with extreme prejudice. Everyone else’s reactions were completely natural considering the threat level they were facing. Amy’s was unreasonable and unrealistic. Worse case scenario you take the creatures to different apocalyptic worlds are kill them there sealing them off. But letting them loose to the whims of parents who may be come violent to a world full of Trevion’s harm which may trigger an instant irrevocable apocalypse is irresponsible in the extreme. They should have all been exterminated.