Who is Bella Swan's enemy?

In Twilight (book one), Bella's enemy is the vampire James, and to a lesser extent, Victoria. In New Moon (book two), Bella's enemy is the vampire family, the Volturi, and to a lesser extent, Victoria. In Eclipse (book three), Bella's enemy is Victoria, and to a lesser extent, the newborn army and the Volturi. In Breaking Dawn, Bella's enemy is the Volturi, and to a lesser extent, Sam's pack.