Thanks for the chapter, that's not a bad finale at all with a ton of new stuff in play. The powers built over the previous arc, and the sacrifices made, did in fact pay off to some extent here. I think that significantly reduces any sort of "no real stakes", literally a Child did in fact die for this and they're still only just getting started. Shirley witnessed what frankly Kate was naive about but nevertheless further underlines Anthony's ruthlessness: a "dummy of chicken and pig" would have massive risk of exposure at even the slightest look. Only a real corpse would do, and while it's not explicitly shown it's probably a child's corpse as well to further the match. Not like they have DNA testing technology or are even doing careful dental checks, and a certain level of rot expected stuff like hair probably isn't a big deal to fake, but an adult who is flat out feet taller or weighs twice as much could also be noticed. They'll have to wonder if someone was killed for it, and it's going to be an going thing between them.
But both of the different Resistance powers got something here as well. Anthony got information and access to a chunk of the Unification catalyst. What plans he has for that will no doubt be a major part of his strategy. He's not stupid, and is taking the darker (but perhaps justified even) path. If he himself is, or he's figured out, what effectively is a "reverse Unification" where they unify but the human consciousness is the one that stays in charge of the final body, that could be the army he thinks he needs. All the raw power to go against the adult Shadows, but on his side.
Kate's side of course got a bunch of new allies, who are in fact firm allies and have never experienced any brainwashing. She now has a real human adult, and one from outside the island. The success will be good for morale, her plan did ultimately work, and if there were things she didn't anticipate, well no plan survives contact with the enemy (or frenemies for that matter) which is also a good lesson. Still feels like she's missing pieces however. They're still operating in the shadows so to speak, in a direct confrontation they'd still all lose. Their intel is still very limited.
Still though onward through the dark maze!