Daniel, of course. He's the single most destructive force in the universe. He opened Earth's stargate, which is the root of all these problems. Along the way, he started a war with the Goa'uld that tore apart the order of the galaxy. A while later, he found the address for Atlantis, exposing a whole new galaxy to havoc and disorder. Not content with that, he had to find yet another galaxy of enemies.