Alan Ryves in The Demon's Lexicon revealing that most of the events of the book were part of his plan to get his brother Nick into a summoning circle, solely for the purpose of setting him free in such a way that no one will be able to bind him again. Alan, you Magnificent Bastard!
And a few minutes before that, he caused a room full of magicians to practically piss their pants by plunging them all in darkness and slowly killing them off, one by one,despite being barely able to run. He does this all by himself even when Jamie and Mae were held hostage, Nick trapped in a barrier, and his own wrists tied up. Badass Bookworm indeed!
Black Arthur gloats about how no one can stop him. Nick's not buying:
Jamie, after spending most of The Demon's Covenant looking like he's going succumb to Gerald's attempts to turn him to the dark side: "There's something you never understood, Gerald. You never had a chance."
And then, after Gerald loses it and starts charging magic like there's no tomorrow, vowing to take Jamie with him by force, non-magic Mae sets out to save him with nothing but a knife. Before she can attack him and almost certainly get herself killed, their mum Annabel appears and smacks Gerald on the back of the head with a golf club, saying: "Get away from my son." Doubles as a Crowning Moment of Heartwarming as it came within ten minutes of Annabel freaking out and driving off when Jamie revealed his magical powers to her.
Jamie: Mum is kind of badass.
When Alan's leg was healed for a while, he and Nick were doing classic back-to-back badass!
Mae in The Demon's Surrender in general; as Sin notes, Mae is someone who knows how to organize and make plans. Her big move in the book, pretending that the Demon's Mark on a magician gave the magician control of the demon, turns out to be a gambit on par with Alan's in the first book. It allows the Market to take over the magicians' circle and completely dismantle it. This is after she uses her smarts and the few resources she has to avenge her mother's death.
Nick's duel with Helen on the Millennium Bridge, some of the most visceral writing in the series with two very skilled knife fighters going at each other with everything they've got.