I like Charlie Jane’s post at io9 on how to avoid the too-many-supervillains problem, but I want to offer a slight variation on two of her proposals for how to solve it. She suggests:
It’s not the number of villains, it’s the number of stories. There’s a limit to how many subplots your average movie can contain, especially subplots which are about the villains of the movie. In the end, the antagonists of the movie have to tie into the main storyline, and there has to be one of those. So if there’s more than one villain, the villains still have to work together as part of the central story, thematically and from a plot standpoint. The Dark Knight does this brilliantly, by making the Joker’s effect on Harvey Dent a central part of the film’s arc…
Each villain is a different lesson. This is another way to go — it’s a bit of a cliche to say your enemies are your best teachers, but it’s still definitely true. And if you’re going to go having more than one villain in a film, then each villain ought to be teaching a different lesson — or at least, a different version of the main lesson. Maybe there are different weaknesses that each villain plays on — or different wrong-headed ideas on the hero’s part that each villain represents.
I’d suggest more specifically that it’s a matter of figuring out what the core issue in a movie is. Spider-Man 3 is exploring two totally divergent issues: the question of whether power’s made Peter Parker a jerk, and the issue of whether his narrative of his origin story is true. These are both full-sized stories that could interlock, but aren’t made to, and as a result, the movie feels squashed. Thor, by contrast, is a movie about one issue, the responsible use of power, but the multiple obstacles Thor faces are all ways to explore that issue. The Dark Knight is about the failure of institutions and norms, all of which are tested in different ways by the Joker, the police department in Gotham, and ultimately even Batman himself. The X-Men movies, which use huge teams to explore the notion of citizenship, have always understood this incredibly well: every character on both sides represents a facet of that ancient argument between assimilation and separatism. The point being: pick your issue first, and the best villain or villains to explore it second. And as a side note, I’d really like to see some superhero movies from the villain’s perspective.