Clex

Clex is the slash ship between Clark Kent and Lex Luthor from the Smallville fandom.

Canon
Clark Kent and Lex Luthor have a complex relationship that began as a close friendship and moved steadily toward mutual enmity.

In early seasons, they often bonded over being the odd ones in a town like Smallville. And often went to each other for advice. Jaded by his father's upbringing, Lex seemingly saw Clark as the personification of everything a person should be and a direct contrast to his own destructive and self-serving youth. He also idolized Clark's relationship with his father, seeing it as something he would love but would never obtain with his own father, even sharing his regrets about his relationship with his mother with Clark. Clark viewed Lex as worldly and informed, quickly misjudged and intriguingly out of place in the small country town. Clark was impressed with Lex's experience and maturity. He frequently took advice from Lex, particularly concerning the troubles in his love life, as he yearned for Lana Lang, despite her dating a boy named Whitney Fordman. Lex often went out of his way to help his young friend win the heart of his childhood crush, Lana Lang, even when Clark didn't ask for his help. He actively prodded Clark into being more assertive with Lana, because he felt this was what a good friend did. Lex said he considered Clark much like a younger brother, trying to use his influence to improve Clark's quality of life.

Clark's serects were a central and contentious element between the two men as they eventually drifted apart and became enemies. Although Lex did not exactly know the entire story behind Clark's alien origins, he knew there was something odd about his friend from the moment that Clark saved him by pulling him from the river following a car accident. Lex was sure his car had hit Clark, and was immediately doubtful of Clark's claim that he dove after him. Lex gave Clark the opportunity to share his secret on his own terms as their friendship grew, but often could not resist asking Clark prying questions. Clark used a temporary loss of his powers to "prove" his vulnerability. Nevertheless, Lex's curiosity was not that easily satisfied.

However, there was other factors that drove them apart over time as well. such as: Throughout the earlier seasons he could be seen trying to control Lex's life. Going so far as to close the factory that Lex was in charge of, just so that the entire town would turn it's back on Lex Luthor and force him to leave. He also didn't approve of Clark Kent's friendship with his son. Later on, he was apparently cured of his narrasstism and became "reformed", although there  were many who doubted that he was truly reformed.
 * Lex Luthor's father, Lionel Luthor. Lionel Luthor exbibits all the classic examples of being an narrasstic parent. Typically narcissistic parents are exclusively and possessively close to their children and may be especially envious of, and threatened by, their child's growing independence.The result may be what has been termed a pattern of narcissistic attachment, with the child considered to exist solely to fulfill the parent's wishes and needs.Commonly parents attempt to force their children to treat themselves as though they are their parents' puppets, or else be subject to punishments such as emotional abuse. Within the realm of narcissistic parenting, personal boundaries are often disregarded with the goal of moulding and manpliating the child to satisfy the parents’ expectations.
 * Lex Luthor's struggle with his dark side and failed attempts at trying to do the right thing.
 * Lex's unhealthy obbession with Clark Kent. He collected everything on Clark Kent, which he kept in a large room. The room was like one giant stalker shrine to Clark Kent. Clark was understandably unnerved and uspet by the room when he found it.
 * Other people also plotted to drive the wedge between them apart, as well. There was Brainaic, who posed as a human professor named Milton Fine. He took advantage of the underlying mutal mistrust in Clark and Lex's friendship to seed doubts about each other by planting clues about what the other one was really doing to make it seem like they were hiding things from each other. Brainaic duped the two of them into beliving that the other one was a dangerous would-be conqueror who needed to be stopped at all costs. He compared Lex with violent dictators like Stalin, Hitler or Napoleon, which prompted Clark to defend Lex at the time. However it was enough to make Clark wonder about Lex. Meanwhile,  Lex finally discovered the truth about Clark Kent, having been manipulated by Brainiac. Lex used an orb to track down the Fortress of Solitude, where he confronted Clark. As Clark tried to reason with Lex, it became clear that Lex felt it was his destiny to defeat "The Traveler". Lex expressed disappointment that Clark had never trusted him with this secret, as he felt that he could have helped Clark become a hero, but Lex's actions had proved to Clark that he couldn't be trusted.

Fandom
FAN FICTION
 * Clark/Lex on FanFiction.Net
 * Lex/Clark on FanFiction.Net
 * Superman/Lex on FanFiction.Net
 * Clark/Luthor on FanFiction.Net

AO3

Fanlore

Wikia