Aelita's determination to keep fighting XANA after all that's happened to her, even prepared to fight alone.
This line sells the point really well:
Aelita: I planned to use that man hole over there but I can't climb... there's a factory near her, it's abandoned, I use it whenever (XANA) comes for me.
Gwen: To hide?
Aelita: To fight.
Every time any of the gang discover a new power.
Gotta get XANA props in Ch.2 for taking control of all tech in the city and bringing it to it's knees. Also Duncan and Lindsay grabbing and threatening Chris when Beth, Geoff and the other contestent who weren't in World Tour were stuck in their VR pods and at risk of becoming vegetables.
Gwen, Leshawna, Geoff, Bridgette, and DJ fighting a materialized Tarantula and saving Aelita which how they got into this war in the first place.
The first fight for the TD Lyoko Warriors, they took care XANA's new monsters in both worlds, even Aelita and XANA admitted that they were pretty good for beginners.
Chapter 30 is one extended CMOA, one that took almost three weeks for the author to post. And man, was it worth it.
In Armageddon Part 2, Trent gets a long-deserved one when he attacks Nephilim after the latter hits Duncan with Laser-Guided Amnesia. It really shows that despite their history, Trent isn't a complete Green-Eyed Monster towards the guy.