After Alternate Milla dies and Milla Maxwell returns to the prime dimension, she quietly reunites with Jude and then unleashes the Four upon Rideaux, pulling no punches and showing that she's just as strong as she always was. In the fight proper Rideaux is weak to the Four's elements, meaning that Milla will be your heavy hitter for this fight and this is her time to shine. To add onto all of that this fight has a unique boss theme that doesn't play anywhere else in the game.
The pre-battle cutscene in Chapter 12 between Ludger and Victor is pretty awesome, and is one of the best-directed action sequences in the entire Tales franchise.
During the second battle with Chronos, Ludger, Milla, Muzet and Gaius all manage to impale Chronos at once on their weapons. It's just too bad that the bastard can reverse time to heal himself...
Bisley Bakur manages to scare off Chronos, something that even the main party hadn't accomplished yet. And before the Final Battle he manages to break out of one of Chronos' prisons and incapcitate the Great Spirit of Time himself. He might not be a nice person but Bakur is a bonafide badass. It helps that he has a chromatus just like Ludger.
When you reduce the final boss' HP to zero, Ludger automatically goes into full chromatus regardless of your meter and then lets you wail on him indefinitely until you finish him off with your new Mystic Arte. Was the final boss giving you trouble? Give him a few more extra hits just for the Catharsis Factor.
The Xillia crew includes a Badass Normal from another world, a girl with an overdeveloped mana lobe even Maxwell recognizes as a genius, a General who controls battlefields like conductors control symphonies, the daughter/student of a legendary staff fighter, and a pair of Physical Gods alongside their equally powerful human companions. Ludger kills them in the Julius Ending. ALL of them. Alone.
Considering that his alternate universe counterpart Victor also did the same thing in his world, that means Ludger killed the entire Xillia party twice over. Ludger may very well be the most powerful Tales protagonist to date.