Lysander and Tancred rescuing Charlie from the ruin during the ruin game. The storms and spirit ancestors that they summon manage to spook Manfred and Zelda so badly that they are still not themselves for over a week afterwards.
Paton Yewbeam in the first book of the series, when he blows up the lights at the school to force Bloor to hand over Emma's birth certificate, and walks away laughing after he does.
Also when Paton BLOWS UP a sewing machine, kills a 100 year old shape-shifter, and burns down his evil sister's house, all in one shot.
The 'night of wind and spirits' in the third book has quite a few awesome moments:
Olivia confronting Belle/Yolanda in the girls' dormitory, and Emma trying to help her.
When Tancred, Lysander, Billy, Charlie and Gabriel face Yolanda, she tries to hypnotise them and shapeshift at them, but they never freeze (well, except Tancred, who's afraid of spiders). In fact, the most awesome moment has to be Gabriel running at Yolanda after Tancred freezes.
In the fourth book, the act the good endowed children and Paton pull off to rescue Billy from the Bloors and restore the balance among the endowed children of the Red King.
In the fifth book, ten good children banish Count Harken from the city by walking hand in hand around the tree that is the Red King.
Emma flying out of school when Tancred is being drowned by Dagbert to get Mr Torsson to rescue him.
Mr Torsson breaking into the school to rescue his son also bears mentioning. He breaks down the main door to the Academy and storms down into the Art basement, creating a mighty big storm and causing chaos in the school. No one can stop him, not even the Bloors. He then confronts the Bloors, with his son in his arms, and yells that they'll pay for what they've done.
Anything involving Lysander and his African ancestors counts as this. Those ancestors are enough to terrify the Bloors and stop them from doing anything.
Due to his powerful hypnotic ability and status Manfred is able to bully just about anyone and get away with it. He's easily able to read Charlie's mind and disconcert him in their first meeting. However just a year later when he tries extracting information again Charlie not only manages to resist him, but steal one of Manfred's memories. Not only that, but later its revealed Charlie's pretty much broken Manfred's hypnotic powers for good.