I watched the movie The Devils Advocate tonight but could not understand why did the satan(played by Al Pacino) choose Kevin(played by Keanu Reeves) to make him a conscientious person. A satan does not do that(making a person good). I admit in the dream he tried to make him bad, but I sensed that satan had had a bigger plan, that is to make Kevin a good person, free from all types of greed. But why did he want to do so? And Why Kevin and not some random person? Is it because he is really his son? But given the fact the whole thing was in dream, I believe the son thing was just part of the dream. So what is the actual reason then?
Satan's aim wasn't making Kevin a good person at all. His ultimate goal was creating the Anti-Christ, a supernatural being who would lead Satan's war against God. To do that he needed two of his children to conceive a child, that child would become the Anti-Christ. That's why he engineered that two of children, Kevin and Christabella (Connie Nielsen), get together. Kevin committing suicide put a monkey wrench in Satan's plans (cue Satan screaming his head off).
Then we see Kevin wake up back at the courtroom. Whether the preceding was a dream, or whether Satan used his powers to reset things is up to interpretation.
But what is apparent is that Satan hasn't given up on corrupting Kevin. He comes to him again, this time in the guise of a reporter who is promising to make him a star for his sudden courtroom performance. While Kevin did the right thing in court (as opposed to what he did in his past iteration), he is still vulnerable to his own vanity. Thus Satan's closing quote: "Vanity! Definitely my favorite sin!"