How does Polidori’s Ruthven compare and contrast with the earlier vampire legends that Polidori describes in his introduction to The Vampyre?

In the stories about vampires that Ianthe tells, there is no way to kill a vampire described, which is crucial in later vampire stories. How does this omission shape struggle of Good Versus Evil?

Why is Ruthven seemingly limited to only women victims? How do his predilections reflect the themes of the story and its cultural context?