Running neck-in-neck with the desire for a friend is his burning need to poke at, understand, control, manipulate and take advantage of everything that comes across his way. Lex, like his father, strives to be the master of his own fate, and understands that total self-mastery requires dominion over his external circumstances as well. To control his destiny he must control his environment. To control his environment, he must understand it and all it contains. He needs to know everything. Anomalies pick away at him like an unreachable itch.
Lex is in many ways the anti-Clark. He is crafty where Clark is simple, cunning where Clark is kind, bald where Clark is shaggy (though he seems to have recently gotten a haircut), haughty and confident (understandably, mind you) where Clark is humble and unsure. Lex is a young adult full of cynicism; Clark is a high-schooler with a basic belief in the good intentions of all persons. Both, however, are extremely good at what they do. And both are destined for greatness of one sort or another.
Lex firmly believes in his destiny, too. He just believes that it is a destiny he will create himself. A defining exchange:
In a complex chess game of counter-machinations, he has destroyed a Luthorcorp competitor by allowing the competitor's CEO's daughter to "steal" a false report that lead to the making of a financially suicidal investment. The daughter was also sleeping with Lex, claiming to want to work with Lex to thwart both of their fathers. Also, the investment was intended (by the daughter and her father) to be the move that would lay Luthorcorp prostrate and ready for a takeover. Anyway, upon discovering the counter-betrayal, the daughter said:
"Lex, we could have been great together."
Lex's response: "I plan on being great all by myself."
It was a defining moment. Not only does Lex declare his life-view, but he also manages to: a.) win his father's tainted respect, b.) increase his power in the corporate world, c.) avoid a trap set for him by a competitor, and d.) punish a person who had dishonestly masqueraded as a friend.
That is Lex in isolation. Put him together with Clark and things get wonderfully interesting.
Way back at the beginning of the series, Lex was in a car accident and drove off a bridge. Clark, who was nearby, dove in, pulled Lex from the car, and saved Lex's life. Or so Clark claims. Maddeningly for Lex, there are incongruencies in this story. Things don't add up. The roof of the car is torn open, supposedly from the impact with the water. He has the car pulled from the water and examined by a cadre of highly-paid-to-keep-quiet experts. Complex computer models are drawn up. Private investigators are hired. He buys off (and employs for himself) a man who claims to have a growing case to demonstrate that Clark is not all he seems. (This last is important, because the "buying off" satisfies all of Lex's conflicting needs: it protects Clark from the unscrupulous guy, it provides Lex with another avenue of information gathering, and it puts Lex in the command chair of this person's life.) Lex also personally - but very carefully - tries to use his encounters with Clark to ferret out the truth.