Lex Luthor has been brought to the big and small screens more than nearly every other comic book villain, but none have done it better than Michael Rosenbaum in Smallville. Rosenbaum's take on Lex Luthor debuted in the pilot episode of The WB series, becoming a key part of Smallville, which put a significant amount of emphasis on Clark's ever-changing friendship with Lex, and how it evolved as Clark grew closer to becoming Superman, and Lex grew closer to becoming Superman's biggest enemy.
Rosenbaum is one of many actors to play Lex Luthor. In the original Superman movies starring Christopher Reeves, Lex Luthor was played by Hollywood star Gene Hackman, whose version was long considered definitive. Others have played the role as well, including John Shea (Lois & Clark: The New Adventures of Superman), Kevin Spacey (Superman Returns), Jesse Eisenberg (Batman v Superman: Dawn of Justice), and most recently, Jon Cryer (Supergirl). However, the most memorable version of Lex Luthor is Smallville's Michael Rosenbaum, who brilliantly captured the qualities one should expect from the Man of Steel's most hated enemy.
Rosenbaum was a series regular for seven seasons, and then returned to play the character one last time in the Smallville series finale as Clark finally completed his ten-year journey. He brought the smugness, the intelligence, the intensity, and the sinister charm needed for a character like Lex Luthor. And unlike some live-action adaptations, Smallville and its cast of characters had the benefit of a TV format and multiple seasons. Smallville gave Luthor a chance to grow, just as it gave fans a chance to see who Luthor was before becoming the mastermind everyone knows him to be.
Smallville was able to take a pure evil criminal genius and make him into a "human" character who viewers could understand and even relate to. Rosenbaum's Luthor was an extremely intelligent, curious person with an unquenchable thirst for knowledge. He wasn't evil by any means, but the potential was always there, which was hinted at in certain, dark moments. In the beginning, Luthor genuinely liked Clark and deeply valued their friendship, despite the fact that Clark was hiding something from him. Another problem with Luthor was his relationship with his father, a person whose love he always wanted but didn't believe he could ever truly receive.
His problems with his father and Clark's inability to return the trust that Luthor had placed in him led Luthor to make morally questionable decisions. As Smallville progressed, Luthor slowly evolved into the villain from the comics. His transformation became complete in Smallville season 7 when Luthor ruthlessly murdered his father and said the perfectly written line, "I was raised in your shadow. Now you're going to die in mine."
Luthor's change from bad to good never felt rushed, unearned, or abrupt. With seven seasons, Smallville was able to take the time to properly build up the character in a meaningful way that paid off. The result was a believable, well-polished villain with clear, understandable motivations and a dark intensity that was incredibly entertaining to watch.