I’m frequently surprised when reading scripts to find that there is no antagonist in the story at all. Sometimes I read scripts where the antagonist role is divided among multiple characters who cause various problems for the protagonist. The best rule to follow is that there should be a single character whose primary (if not sole) function in your screenplay is to prevent the protagonist from accomplishing his external goal. First I’ll tell you who the antagonist should be, then I’ll tell you why there should be a single antagonist, and finally I’ll tell you how the antagonist should stop the protagonist from achieving his external goal. Don’t you love it when advice gets this specific?
So who should your antagonist be? First, he should be demonstrably more powerful than your protagonist. If you put the two of them into a room together, the audience should have no doubt that the antagonist would kick the protagonist’s butt ten times out of ten. Also, do you remember how I wrote in a previous post that your protagonist must have an internal flaw that makes his external goal particularly difficult for him to achieve? Your antagonist should have the most intense possible version of that same flaw and he should revel in it. A great example of this is in “The Dark Knight.” Batman is an outsider who doesn’t fit into normal society, and who is rejected by society despite his efforts to help people. By contrast, The Joker is a big ol’ freak who takes full advantage of his outsider status to do whatever he wants. Plus, his willingness to ignore rules and not care whom he hurts makes him much more dangerous that Batman.
Next, why should there be just one antagonist? A good screenplay is about a protagonist’s attempts to overcome his internal flaw in order to accomplish his external goal. The best way to visually represent whether or not your protagonist succeeds at these attempts is to have him do battle with a single, powerful character who perfectly embodies his internal flaw and whose sole purpose in life is to stop your protagonist from achieving his external goal. If your protagonist defeats that kind of antagonist, the audience will know without any doubt that he has grown dramatically since the beginning of the story. You can –and should– have many characters who cause problems for your protagonist, but make sure that there is a single antagonist who is in charge of stopping his external goal.
Now I’m going to contradict myself by saying that it’s possible, and sometimes even preferable to have more than one antagonist. Lemme ‘splain. As I said, there should be someone in your story who opposes your protagonist’s attempts to achieve his external goal, but there should also be someone who opposes his attempts to overcome his internal flaw. It’s nice and simple when that’s the same person, but it’s often two different people. If your primary antagonist isn’t opposed to your protagonist’s internal flaw, then you need to have a separate internal antagonist whose job is to prevent your protagonist from overcoming his internal flaw. When your protagonist defeats that character, then the audience will know that he has overcome his flaw and is well on his way to achieving his external goal, if that’s how you would like your story to end.
In “Juno,” both the external and internal antagonists are portrayed in the single character of Mark Loring, though Bleeker is also a bit of an internal antagonist/punching bag as well. In “Fargo,” Jerry Lundegaard’s external antagonist is chief of police Marge Gunderson, and his internal antagonist is his father-in-law, Wade Gustafson. When Jerry fails to defeat his internal antagonist, we know that he’s in serious trouble, which happens immediately when Carl gets away with all of the money. It’s fine either to have one antagonist or to have separate external and internal antagonists, as long as you have somebody opposing your protagonist’s attempts to accomplish his external goal and to overcome his internal flaw.
So now that you know who your antagonist should be, let’s talk about how he should defeat your protagonist (which should happen at the end of Act Two and possibly again at the end of your story). The first big thing that your antagonist should do at the end of Act Two is to expose your protagonist’s internal flaw for the whole world to see, or at least to the person that the protagonist has been hiding it from – probably a love interest, but you can make it anyone you like as long as the effect on your protagonist is devastating. Then you need to think of the worst possible thing that could happen in the protagonist’s pursuit of his external goal, and have your antagonist do that. In “Juno,” (Spoiler alert!) this happens when Mark announces that he is going to leave Vanessa, thus making it impossible for Juno to achieve her goal of finding a great couple to adopt her baby. This event, along with the fight that Juno has with Bleeker, causes her crisis of faith in humanity, so she has to consult with her father/internal mentor in order to figure out how to proceed. Once Juno has rejected Mark, thus removing him from the picture, she is able to figure out the right way to proceed with her external and internal problems.
The bottom line is that you must must must have a single person whose primary job is to stop your protagonist from achieving his external goal, and then either that person or another person needs to oppose your protagonist’s attempts to overcome his internal flaw. There’s no rule about when the antagonist should first appear in your script, but I think it’s best to introduce him in the first act. I’ve seen it happen at the first plot point, as it does in “Fargo,” and sometimes even as late as the mid-point, but the earlier that the antagonist shows up in your script, the sooner he can start making your protagonist’s life miserable. Happy antagonizing!