Based on another question, What was Satan's goal with Kevin?, the answer says that Milton/Satan/Pacino is trying to do everything again, taking a different approach.
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!"
Was this the movie's intent? Is there any Word-of-God (pun totally intended) evidence for this, that Milton was trying again? Or is it that he decided to leave Kevin alone (My personal interpretation of what happened at the end)? Or did they intentionally leave it up to the audience, so there is no actual answer?
And if so, does that mean he has tried or will continue to try again? Was the version we see in the movie his attempt to cause Kevin to sin via Greed, one of the 7 deadly sins? Then the second teased at the end to sin via Vanity, another of the 7 deadly sins (Vanity is also named Pride). Did Milton try before or will try again with the rest of the sins?