As anyone who watched the episode knows, the cloned Lex Luthor has become his late teens/early 20s version as portrayed by Lucas Grabeel. Following some genuinely powerful scenes between Grabeel's Lex and John Glover's Lionel Luthor, there is a "quieter" moment between Lex and Tess in which he complains about feeling sick, and also that some of his memories are beginning to fade. Tess, well aware that no matter what she does, ultimately Lex is going to become his evil self (after all, he has all the memories of his progenitor), attempts to secretly inject him with something that will either render him unconscious or, more likely, kill him. But when she attempts to administer the shot to his neck, the needle breaks, unable to penetrate his skin.
Hmmm.
The first thing that instantly comes to mind is the notion that this Lex has been cloned from DNA taken from Clark. So, in an interesting twist on the DC Comics approach in which a clone of Superman (now known as Conner Kent) is created from the DNA of the Man of Steel mixed in with Lex Luthor, this time the DNA cocktail has been used to create a clone of Lex.
What this would potentially give us in the final episode of the series, is a super-powered battle between Clark and Lex, the years of frustration and animosity between them finally being given the opportunity to be unleashed. In fact, one could easily see Clark defeating Darkseid - his greatest moment - putting on the Superman uniform and THEN having to face the super-powered Lex in a battle that will establish a future history between these two incarnations of the characters that will only exist in our imaginations.
And as to the memory loss Lex is experiencing -- what better way for he and Superman to be enemies than for him to have forgotten all he knows in terms of the truth about Clark and the Kent family? At which point, the playing field would be cleared, all of the pieces would be in place and things can continue off camera.
All conjecture, of course, but what do you think? Any of the above make sense? Please sound off below and offer your own theories as to what may be happening.