In "Fight to the Finish", Jeremie made a multi-agent (MA) program that wiped XANA out. In a few Fan Fictions, XANA is made a good guy.
There is one. It is called Code Lyoko: Fall of XANA.
The story of the discovery of Lyoko is covered in the 2 part episode Xana Awakens. It can be found on YouTube by searching for 'Code Lyoko XANA Awakens'.
xana kissed Aelita on episode 43 xana's kiss
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Code Lyoko - 2003 Xana Awakens Part 1 was released on: USA: 2 October 2006
Code Lyoko - 2003 Xana Awakens Part 2 was released on: USA: 3 October 2006
Code Lyoko - 2003 Xana's Kiss 2-43 was released on: USA: 7 October 2005
XANA doesn't stand for anything, it is a computer program to stop Project Carthage.
Xana Awakens part 2
William is the last tool that Xana has. After Jeremy frees William in "Down to Earth" XANA only has his monsters left. He doesn't have anyone on Lyoko like William anymore.
In the episode Laughing Fit. Xana posses laughing gas and uses it to attack the lyoko gang.
Xana is defeated and the Super Calculator is shut down