Rose cutting off two Strigoi's heads. With a DULL SWORD.
Rose and Christian teaming up together and fighting Strigoi near the end of Shadow Kiss.
In Spirit Bound: Rose, Lissa and Eddie managing to break Victor out of a high security prison.
Lissa punching Reed Lazar in Blood Promise.
Lissa staking Dimitri in Spirit Bound and turning him back into a dhampir.
Mia, a Moroi who has never practiced offensive magic, successfully distracting a really old, really powerful and really badass Strigoi during Frostbite.
Even though Dimitri turns Strigoi and Rose thinks she kills him he manages to send her a letter including the stake that Rose stabbed him with, and Strigoi can't even TOUCH stakes and promises that Rose would see him again. Definately a Crowning Moment of Badass for our little Dimka.