At the end of the devil's advocate movie?

The purpose of the ending was to show that no matter what you do, you always run the risk of sinning. In his case, his weakness was vanity and milton played him into taking the interview, and that would male him a star, instead of a successful lawyer. He knew that his client was a child molester, so by refusing to help him in court, he prevented the child being molested, killed and put in the trunk. Absolutely great movie.