Really if you think about it though, some of the greatest villians ever were eventually defeated by some really small act. In LOTR, Sauron was taken down by a ring being thrown into a volcano. In Star Wars, the emperor was destroyed by being flung over a railing. The Wicked Witch of the west melted from a little bit of water.

These villains are always touted as being all-powerful and unstoppable but the good guys have to win eventually so the writers must give them some way to be defeated.