Even the opening goes out of its way to show how badass MillaMaxwell is: even if you choose Jude, Milla is still shown making her Heroic Sacrifice. And if you choose Milla's? Instead of seeing Jude attacking some aquatic mooks, Milla is shown going toe-to-toe with THE Big Bad, Gaius...and not only managing to get into a bladelock with him after he effortlessly punts Jude aside, it's implied MILLA is getting the upper hand. Milla, YOU are a badass.
Some clarification here. During the part where Jude "smacks some aquatic mooks", Millas opening has her (and Jude) fighting a flying monster. And while Jude is quickly taken out of the fight in Milla's fight with Gaius, Milla isn't even there in Jude's, and Gaius can't land a single hit.
Let's also give Milla credit for cleaving an enormous serpentine creature in half during her opening.
At Bermia Gorge (Jude's Route), the group are pinned down by snipers, and can't get a clear shot at them - so they need a distraction. While Jude draws the attention, Milla sneaks off for a surprise attack, and a sniper aims straight at him and fires... inches from his face, with no change of expression or flinching, Jude moves out of it's way with little effort, without even taking a step. The sniper can't believe it, but the player knows how fastJude can move. On Milla's Route, his moment is replaced by a simpler-but-stil-awesome one for Milla, easily sneaking up on the same assassin and knocking her out while she was distracted by Jude, who didn't sense her at all.
Jiao's Dying Moment of Awesome. He takes tons of hits from Spyrix weapons and is still standing with no trouble, says his final words to Elise, saves Gaius one last time and silently tells Gaius to leave him behind. Gaius thanks him for his faithful service and the other Chimeriad say their silent farewells and after using his Mana Lobe's full power, he wipes out the entire army of soldiers there before needing to be taken down by shots from an airship.
After Milla gets blown up, she travels with Leia and Jude to find a spirit fossil to power an aspyrixis, a medical device that will allow her to walk again. It's heavily implied that the device works by directly connecting with neurons, and it is described to be incredibly painful. So Milla, Leia, and Jude make it to the bottom of the mine and find a spirit fossil, then are immediately attacked by a giant caveworm thing. Leia and Jude are staring down defeat, when the spirit fossil falls a few feet from Milla. Milla proceeds to crawl to the spirit fossil, connect it to the aspyrixis, and while in incredible pain and running on nothing but raw adrenaline, rushes into battle with a scream to protect Leia and Jude.
Then the most awesome boss battle music kicks in as you face it down.
When Jude's in his Heroic B.S.O.D. after Milla dies from a Heroic Sacrifice, Leia sticks with him the whole time caring for him and once Alvin attacks him, Leia immediately drags Jude away by the hand and ends up holding her own really well against Alvin until Jude snaps out of his Heroic B.S.O.D. and Leia is shot by Alvin.
Jude then immediately snaps and charges at Alvin and a battle between them happens with Alvin ranting about how Jude's pissed him off from day one for being an idealist and the honors student, Jude replies with "What did you want me to do?!" and if the player wins the fight, Jude ends up beating up Alvin and gives a speech about Milla dying for them and how they need to do things without relying on Milla.
To put it simply, ANY scene where Milla is doing something other than talking (And even then, in some scenes where she is) is pretty badass.
Perhaps one of the greatest examples is HOW Milla lost use of her legs: She ran at Nachtigal, where her leg brace blew up point-blank. Then, she gets up anyway. At this point, Nachtigal himself looks FRIGHTENED by the sheer willpower this woman has, and rightfully so, as, even as it seems the second explosion really did do Milla in... she jumps through the and smoke and still tries again. And Nachtigal himself, after seeing Milla did indeed lose consciousness this time, says aloud he had not gotten injured at all - but it's clear that he is still very shaken up.
Another great example is when Milla, having literally disintegrated into nothing, lost her memory in the Spirit World, and can barely speak outside of a few lines in battle... takes on and beats Muzet, who could hold her own against all five of the others. But that's nothing compared to her next act: essentially willing herself back into existence, then follows it up bydestroying God's barrier with one sword slash. That's right. No body, no physical presence, no proof she ever existed outside the spirit world and outside the memories of the people she had met...and she COMES BACK.
Jude and the rest of the party getting back up from the No-Holds-Barred Beatdown the real Maxwell is giving them, telling him to shove it. Compounded by Jude, the "Honor student", calmly standing while Maxwell bombards him with elemental Beam Spam, walks forward without stopping and then RUSHES him, throwing a well-deserved Megaton Punch at the Physical God. Jude, you are a badass.
And thanks to Milla's interventation (see above), just as Jude makes contact, the barrier shatters - and it connects, sending Maxwellflying.
The war game played between Rowan and Wingul. Wingul intentionally chose the only battle Rowan 'tied' on. Rowan proceeds to win without attacking a single enemy soldier.
Not quite as explosive as the rest of these, but apparently Elize took down two Aquadragons. By herself. After a day of extremely intense fighting in a war and the death of the man who had essentially been her father figure. And it still makes sense, because gameplay-wise, that's around the point where she starts unlocking absolutely murderous darkness-type spells and the ability to occasionally resurrect herself whenever she feels like it. Elize is Little Miss Badass, no question.