From LEGO Batman Wiki
When Luthor was a teenager, his family moved to Smallville. He became a fan of Superboy, who built him a laboratory in gratitude. There, Luthor studied on how to make artificial life and make a cure for kryptonite poisoning. Unfortunately, the lab caught on fire and during a rescue attempt by Superboy, chemicals spilled on Luthor, making him bald and destroying his kryptonite cure. He later became Superman's arch-enemy.
Luthor comes to the fifth Man of the Year ceremony held in Gotham City, where he loses to Bruce Wayne,, much to his disappointment. However, the ceremony is cut short by the arrival of The Joker, Harley Quinn, Two-Face, and The Riddler. During the robbery, the Joker steals Luthor's watch. After an extended chase, Batman and Robin manage to apprehend the Joker and his comrades, and they are returned to Arkham Asylum. Unfortunately, Lex Luthor gains an interest in using the Joker's laughing gas for his own needs, and breaks him out of prison with his new weapon, the Deconstructor, which breaks apart metal objects. The Joker agrees to help Luthor and the two escape in a helicopter, but not before the Joker frees the other inmates of Gotham City.
While the Dynamic Duo deal with the other escaped criminals, the Joker and Luthor invade the Ace Chemicals Plant and cause a fire, which Batman and Robin investigate. The two are nearly killed until Superman rescues them. After Superman leaves, Batman and Robin chase Luthor and Joker through Gotham City. While Luthor's LexBots fight the duo, the Joker make fake kryptonite. Batman and Robin confront the two criminals but the Joker subdues them and throws them out of Luthor's Juggernaut, and uses the Deconstructor to destroy the Batmobile. Batman takes the fake kryptonite to the Batcave, where he finds out it is a tracking device. Immediately, Lex Luthor and the Joker attack the Batcave, using the Deconstructor to destroy their vehicles and sending the LexBots and the Joker's goons to attack the duo physically. Luthor manages to steal the kryptonite hidden by Batman and retreats, leaving the Batcave on fire. Fortunately, Superman saves the duo again.
Luthor and Joker fly to Metropolis in an aircraft, but are followed by Superman and Batman. The two destroy the aircraft's defends and manage to find Joker. However, he uses a trap door that causes Batman to fall out of the aircraft, forcing Superman to rescue him and allowing Luthor and Joker to escape. Finally reaching Metropolis, Luthor consructs a giant robot. When Superman and Batman find him, he reveals that he plans to use the Joker's gas to mind-control the citizens of Gotham to follow his command. He then apparently kills the two and flies off to Gotham City. However, Batman and Superman had switched suits and are on the robot's trail. After finding out that the two are alive, Luthor deals with Superman himself and weakens him with the kryptonite, knocking him out. He then tries to shoot Batman but misses and he jumps off the robot and saves Superman. The robot, damaged by Superman, falls out of the sky and crashes.
Superman, who has been weakened by the kryptonite, can't fly and the robot attacks them, knocking them into the sewers. After sending Joker Goons and LexBots to attack them, the robot uses the gas to mind-control the people. However, Superman and Batman interrupt the robot and damage it further, enraging the Joker to the point that he uses the Deconstructor on Batman. However, Robin saves him and the robot chases them through Gotham City. However, Batman has tricked the villains and they are seen on a giant tv, which alerts the Justice League of the robot. In response, the robot climbs to the top of Wayne Tower, where Batman, Robin, Green Lantern, and Cyborg knock it off the tower. The robot is destroyed upon impact, and the Joker is knocked out while fighting the League. However, Lex Luthor comes out in a smaller robot, and fights the League. However, he is ultimately defeated when a laser from the Justice League's tower zaps him and destroys the robot. He is then sent to jail with the Joker.
He can later be found and fought at the Yatch Club, where he can be bought if defeated.
Lex Luthor's main weapon is the Deconstructor, which can destroy Batman, who wears a black suit. While in the Power Armour robot, he can fire the Deconstructor, can fire bullets, and shoot missiles.
Luthor is bald, and usually wears a black business suit witha tie.