I think the reason I like this is the whole yin and yang aspect of the pairing.  They're total and complete opposites, but Jeremy can give himself XANA's powers if he sits down and works it out (like activating the towers).  Plus XANA's habit of copying Jeremy multiple times in canon.  (Three times to date!)  They say imitation is the highest form of flattery.  Plus even though they're opposites, they're identical in the way that they're not usually on the front lines themselves, ordering their troops about on the battlefield of Lyoko.  In addition to that their determination and intellect is the same.  It kinda makes you all goosepimply.

But enough of my rambling!  This chapter was superbly written.  I love your characterization of XANA.  It's almost as if he's becoming a (if somewhat smarmy) human.  And I was shocked that he was actually offering to help.  Meanwhile Jeremy remains separated from the pack and constantly assaulted by his enemy.

I saw some minor grammar mistakes but not enough to really bother me until this sentence:

His eyes darting to XANA with bottled thoughts of bloody work. 

Maybe I'm just not on the ball today, but that sentence threw me for a loop and out of the moment.  On the whole though, great story.  Solid ten.