Finagle's Law meets the Rule of Drama. Any time the villain is putting together an Evil Plan, we can always expect it to reach its final stage, no matter what the hero or heroes do to try to stop it. If the villain is trying to collect the Three Cosmic Keystones that will allow him to become a Physical God, he will assemble them all. If the villain is trying to unseal a Sealed Evil in a Can, it will break free and need to be defeated or re-sealed. If the villain is planning to disgrace the king, Hypnotize the Princess and rule the kingdom, he will accomplish the first two before The Hero stops him. And so on.