And NO ONE has mentioned Dan's CMOA in Book 8? When the Jonah Wizard and his parents try to tell Dan that he's a Janus, Dan yells, "I'm a Madrigal!" at the top of his lungs. That may not seem so impressive, but when you read the book and realize that he's doing this to show the Wizards that he's a wild card, that they don't own him, coupled with the awesome writing...
Amy smashing the master serum vial over Isabel's head.
Amy: Don't hurt anyone in my family ever again!
Isabel drinking the master serum in Day of Doom after her daughter's death, utterly pwning every Vesper in the room, then going down in a blaze of glory by defeating Damien Vesper. Just... wow.