Theo standing up with a huge hole for a lower torso, telling Jetta "not quite" when she says that he should be dead.
Both Theo and Julia got their moments in the "Dark Home" storyline. Theo: "Correction number 2: I don't always block." And Julia schooling a very smug Zero after not falling for his trap.
Then, of course, the bad guys have their own CMOA, when the heroes foolishly attempt to fight them in their sanctum sanctorum. Two words: Perfect Summon.
Ancient Gina pulls this off against a queen Abyssalisk by combining her allies' powers into an Infinity+1 Sword attack that disintegrates her own arm up to the elbow. (She heals it almost instantly, but not before Brit' notices.)
Gina's fear that Madrid, who has no combat skills to speak of and was unarmed, would overpower Penny, Lynn, Subtracto and Kahn (who is pretty much unbeatable in the Library of Time) and kill her. Gina demonstrates this by using a Post-It note and a pen to take control of Khan's body. Madrid then leaves in a way that shows she could have killed Gina all along, making her realize she might have been overreacting.
Julia's showdown with G'nolga at the Tournament of Arms. All of it.
Britanny's long, long-awaited return to Earth after the Oblivion story arc.
Madrid beating her future self with her own twist on the old Rock Beats Laser trope.