|Family||Lex Luthor (good side)|
| Powers and|
|Genius-level intelligence, skilled strategist, heightened immune system, skilled hand-to-hand combatant|
|Played By||Michael Rosenbaum|
|Status||Merged with Lex Luthor|
"I want you to remember that despite all your amazing powers, there was one man that beat you. Maybe this was always our destiny. How sad." - Alexander Luthor, Onyx
Alexander Luthor is the evil counterpart inside of Lex Luthor. This version of Lex was released, due to a burst of energy emitted from Black kryptonite, which split both the good and evil side of Lex.
Due to being an evil version of Lex, it is completely obvious that he looks exactly like him. In Onyx, Alexander wore mainly suits.
Alexander is simply evil and sinning version of Lex. He knows nothing but to do bad things on another person or thing.
Powers and Abilities
Even though all of it wasn't demonstrated in the episode, Alexander had a genius-level intellect and a heightened immune system. He was also both a skilled strategist and is a skilled combatant in fighting.
Lex and Dr. Sinclair are inside a LuthorCorp lab about to undergo an experiment involving green kryptonite. In the experiment, the kryptonite must be super-heated. Unaware of the risk, Lex and Sinclair go ahead, but begin to worry when the kryptonite exceeds its target temperature. After an alarm sounds, Lex shoves Dr. Sinclair out of the way while he is caught in a burst of energy emitted from the kryptonite, which has transformed to black kryptonite. This produces an effect where Lex is split in two - one of which is his darker alter ego. Shortly after falling to the floor, Lex - unaware of his split self - helps up the scientist and brings him to the hospital. Watching the two make off is the evil Lex who is just realizing what has happened.
Clark and Chloe go to visit Lex (Alexander) in the hospital and begin to ask what happened. Alexander says that he'll take Clark to the lab and show him what he was doing. Clark accepts, but Chloe says that she'll stay behind to ask the scientist a few questions.
At the LuthorCorp lab, the good Lex shows Clark around and explains that he has been conducting experiments with plants, trying to get them to grow in the most harsh environments. He gives Clark an apple, but it tastes rotten. Lex explains that even if the plants grow anywhere, they don't retain their usual taste. Then Lex opens a locker containing kryptonite samples and Clark excuses himself, blaming the apple for his nausea attack. In the background, Alexander has overheard the whole conversation.
Later at the Luthor Mansion, Lex is visited by his father, who is arranging a charity fund raiser. Lex agrees to come to the fund raiser, on the condition it's held in the LuthorCorp Plaza. Lionel is surprised by Lex's newfound generosity. When Lionel leaves, Lex walks in and knocks Alexander unconscious. Then he brings him to the cellar, and imprisons him there. He explains he does not know what might happen if he killed him.
Clark walks in on evil Lex, who tricks him into thinking he is the good Lex by talking about their trip to the lab. Clark explains about the split. Lex acts surprised and tricks Clark and Chloe into the lab. Once there, he drops a large block of concrete on top of them. Clark protects Chloe from the falling debris and brings her to the house, while Lex watches. At the house, Clark tries to get Chloe to the hospital but she convince him that she is fine. Chloe questions how they were able to survive, but Clark refuses to come clean.
In the barn, Clark encounters Lex, who tries to coerce him into joining him so they can rule the world together. Clark declines and grips his throat. Lex puts on a kryptonite ring and tells Clark that he knows his weakness. Martha and Jonathan come in and Lex shoots Jonathan in the leg and departs.
After taking Jonathan to the hospital, Clark goes to the mansion searching for good Lex. Using his super hearing, he hears his moans and super speeds to free him from the wine cellar. However, evil Lex expects that and overpowers Clark using his kryptonite ring. Lex and Alexander fight until Clark uses his heat vision to turn the evil Lex's kryptonite ring into black kryptonite, fusing the two Lexes together.