The Serpent's Tale - S2.E26

Lee is chased around Landmark City by Dragon. He ends up in his office in Lee Industries and erases all files on Mu-Team from his computer. Dragon is after those files, so he fights Lee. Lee falls off the roof of the building, his hardlight armor saves him from the fall but his body starts to absorb hardlight. The process is irreversible. Lee also goes back to his "old self". Axel comes to Lee Industries, and Lee tells him that Dragon was Sebastian's clone he had created. Sebastian and Lee were friends, but Lee needed more money for his experiments, so he took it from the Serpent's Tale in exchange for government cloning secrets. Manning caught him and wanted to expose everything, so the Serpent's Tale took him out to protect their money. After that Lee didn't want anything more to do with them, so he quit the project, but the Serpent's Tale sent Dragon to find Lee. Lee regrets his actions, Axel leaves to find The Serpent's Tale leader, who is revealed to be Kuan. Kuan finishes off Lee and attacks the aquatic center. Axel and Kuan fight, Dragon tries to protect Axel, a large explosion from one of the attack's leads to the building being about to corrupt. Kuan and other his henchmen escape but alpha teens can't get out. Lee appears in a form of a ghost made of light and says that "science has given him a means to make amends for all he has done starting now". He teleports the teens and Dragon out of the building which then explodes. The team and Dragon are safe, Lee disappeared, and Kuan, back in his headquarters, says that the fight isn't over yet.