4. Neo vs. Agent Smith (Matrix trilogy)
Agent Smith began as an artificial intelligence program, which is developed to keep order in the Matrix. He appears in all Matrix trilogy films and becomes Neo’s arch-enemy. In the first film, Neo successfully “deletes” Agent Smith, but in the sequels, it is revealed that Smith managed to free itself from the system. As a renegade program, Smith behaves much like computer virus with the ability to replicate itself. It even has the ability to manifest in real world, by infiltrating a human that’s connected to the Matrix.