The beginning of the game. It starts with Lightning vs Caius in Valhalla and you get to fight him as Lightning running across the shores of Valhalla on Odin against Chaos Bahamut, followed by some cinematic scenes with Advent Children physics as Lightning and Caius fight. Then Noel shows up through a gate and Lightning saves him by summoning Bahamut and fights Chaos Bahamut in the air, sends Noel to the past to find Serah as Caius summons a massive meteor. Lightning responds by having Odin throw her into the meteor. And that's just the prologue.
The Final Boss. You start off fighting Chaos Bahamut on Sazh's airship as he flies through the skies of Pulse, then after that we fight Caius on the same airship. Next thing you know, we're in Valhalla where we have to fight Caius twice in the same battle, and then after a short cutscene we have to fight Jet Bahamut, Amber Bahamut, and Garnet Bahamut. That's right, three freaking Bahamuts at once. And to top it all off? Thesethreepieces of music play in the background.
Within the span of one episode, Serah takes on Caius alone and wins, breaks out of her Lotus-Eater Machine with minimal help, and the breaks through time and space to save Noel from his. Not bad for a former dead little sister, huh?
The fact that Vanille and Fang help her break out of it is also really fantastic.
Depending upon how you look at it, the fact that Caius is the first villain in the series to come out on top is pretty cool. The fact that he made a Determinator like give up (albeit temporarily) makes it more impressive.
Noel and Caius' final sword duel on the beaches of Valhalla where Noel makes Caius realize why Yeul chooses to return again and again before delivering a beautiful coup de grace.
The heroes have destroyed the Proto fal'Cie Adam, but a Grandfather Paradox keeps bringing it back. How does Serah handle it? Grabbing her sword and charging it, screaming at Hope that 'his machines are driving her nuts!'It works.
The Coliseum DLC in general. You get to fight some of the great Final Fantasy legends fully rendered in XIII-2's stunning graphics. If you're lucky enough, you can have them on your team from then on out!