Every movie needs a villain because that gives your hero someone to fight against. Most importantly, your villain needs to be someone or something directly confronting your hero.
Think of a bad movie you’ve seen recently and chances are good that it didn’t have a strong villain pursuing a specific goal. In “The Men Who Stare at Goats,” there is no single villain pursuing a goal from start to finish. As a result, the movie lacks a sense of tension and suspense as the characters simply pursue their own goals without any threat from a villain to stop them or urge them forward before it’s too late.
In “Terminator Salvation,” there’s a similar lack of a distinct villain. We know the villain is SkyNet, the self-aware computer, but unlike the first two Terminator movies, the villain isn’t personified as a relentless killing machine that looks like a person. Instead, we get to see random giant robots special effects that look like they were taken from the movie “Transformers” as they threaten the characters. Because of this lack of a single, distinct villain, “Terminator Salvation” winds up being more special effects and explosions with little story, tension, or suspense.
“The Poseidon Adventure” lacked a single human villain, but replaced it with the relentless pursuit of the rising water. Other disaster movies like “The Towering Inferno” duplicated this with the villain as the force of nature.
In “Thelma and Louise,” the villains are the cops pursuing them, but the villain in general are men. We can easily understand how a man can be an enemy to a woman, but it’s much harder to get concerned when an abstract SkyNet computer network is a villain.
In “Wargames,” the NORAD computer was the villain, but the military men gave the computer a human face and made the villain someone we could relate to. The point is that you need a strong villain in the form of a human. The villain doesn’t have to be a human such as the robots in “The Terminator” or “WALL-E,” but the villain must be seen as a single entity like a person. Fighting a killing machine designed to look like a man makes a good villain. Fighting SkyNet, a computer network, is a much hazier and less threatening villain without a human face or single entity we can associate with it. Even in “2001: A Space Odyssey,” the villain is a computer, but is personified by its glowing red camera lens.
Make your villain a person or at least the same size and shape as a person who can directly confront the hero. Audiences can fear villains that are similar to people such as a robot. Audiences can’t feel emotionally involved when the villain happens to be the chemicals in the air, secreted by trees in “The Happening” or some blob in the sky like the villain in “The Green Lantern.” The more human-like your villain is, the more imposing your villain will be to the hero and audience and the more emotionally involved your audience will get.