Selece's revival as a Rune God, where he defeats the Monster of the Week by clasping his hands together.
In the manga, Fuu's battle with Caldina. Her friends have been hypnotized to kill her, so she invents a spell on the spot to bind them. Then when Caldina takes control of her, she breaks the enchantment through sheer willpower and invents a second spell to take her out.
The anime has her inventing only one new spell, but also has Ascot trying to stop Caldina.
Hikaru has one that lasts half of episode 14 wherein she chases a monster that abducts Umi and Fuu. She charges headlong through a forest of thorns, gets knocked into a canyon, falls three times while climbing out, and, despite being quite a bloody mess, still has the strength to take out the monster in one hit from her sword and a magic spell. Determinator doesn't even begin to describe it.
Not only that—she figures out that the monster is able to smell out blood like a shark, so she cuts herself with her own sword in order to make it come back so she can kill it.
Hikaru vs. Lafarga, especially her Badass Boast in determining to win using only the sword. She manages to disarm him, despite the fact that he'd been curbstomping all three of them.
All of the Rune God revival episodes, as well as the first season finale where they combine.
The girls defeating Zagato in the first season finale by combining their attacks.
Debonair's final defeat in the second season finale.
Starting with the most awesome, Ferio, Ascot and Lantis' rescues (or attempted rescue, in Lantis' case) of Fuu, Umi and Hikaru, respectively, in the second season when the girls are captured by the invading countries.