Hugh in Hollow City, when he is the only one not captured by the wights, and saves the rest by summoning several hundred thousand bees (enough to block out the sun) and commanding them to surround the wights and sting them to death.
When Emma finally has enough of Enoch and calls him out on his callousness. It actually makes him pause and choose his words before he says anything else.
Jacob in Library of Souls:
He successfully pretends to be fighting his hollowgast, and when the staging gets out of control, he wounds him so that the situation almost turns into Springtime for Hitler. By accident.
He manages to take control over a dozen hollowgasts and leads them into a giant battle, while in the minds of every single one of them, taking out a small army of wights with his smarts, tactics and overwhelming power, all while riding on the biggest hollowgast's back like some triumphant king.
Bentham has his moments in the same book:
Charging into battle on grimbearback with a cry and rescuing the children from wights.
Hulking out into giant insectoid monster and battling Caul in a kaiju fight that levels the entirety of Abaton.
Staying behind to stop Caul from killing the children and to give ymbrynes time to collapse the loop.
The hollowgast Jacob turns into a pet manages to track Jacob down through half the London and into another loop, and when Jacob orders it to, it brings down the entire bridge with just its tongue.
The Film:
Miss Peregrine herself is made of awesome, but in particular, she gets one for her reaction when Barron shows up at the home with a knife to Jake's throat. Barron tells the children (who are on the stairs watching) to come down- But Miss Peregrine turns and tells him that nobody gives orders to her children. She shushes him when he tries to protest, and when he speaks after that she snaps, "Didn't I tell you to be quiet?" She then proceeds to tell all the children to come downstairs, explaining in excruciating detail Barron's reasoning (he wants her to go with him in bird form so she can be caged, and all of the kids locked in a room so they won't be followed). She does all of this with a completely straight face as though it's a perfectly normal day, despite the fact that she and her kids are all probably going to die, and that these are some of the last words she'll be speaking to them. When she asks if her reasoning is correct, Mr. Barron's Stunned Silence is golden.
The peculiar children bringing a sunken liner back to the surface and using it get to Blackpool.
The children's plan to get rid of the four hollows at Barron's side. First they lure the hollows to the pier, where they bombard them with snowballs and candy, rendering them visible to all. Then Enoch resurrects the skeletal crew of the liner, who then attack the hollows in an EPIC battle scene. They actually succeed in killing off three hollows.
Then Bronwyn pulls off an epic moment by throwing the unicorn from a merry-go-round into the last hollow, impaling it and sending it flailing into the ocean. It doesn't actually kill it but it was still pretty epic.
ALL the children get awesome moments in the climax.
Hugh launching his bees at Barron's cronies.
Fiona throwing seeds at a wight, which immediately sprout into vines that bind the wight.
Olive setting Barron's coat on fire.
A villainous example for the Wight with ice powers. When Olive tries the same trick on him, his peculiarity overpowers hers to the extent that her arm ices over.
Bronwyn throwing a ####### CHAIR at Barron.
Horace's attempt to stop Barron may have failed completely, but you've got to admit, that kid's got balls.
Enoch bringing a giant elephant puppet to life to save Olive.
The twins and Claire have an EPIC big hero moment during the climax. The twins are revealed to basically be mini gorgons. When a female wight tries to attack them, Claire's backmouth bites down on her arm, allowing the twins to turn the female wight to stone by revealing their true (horrifically awesome) faces. The female wight falls to the ground shattering herself.
Jake figuring out how to beat Mr. Barron impersonating him. Pointing out that only he can see the monsters, before the Hollow he's tracking grabs Mr. Barron and eats his eyes.
Jake subverting the running gag of his terrible aim by shooting the Hollow that killed Barron, with only a split second to aim.
