Possible Clues:

• Storybook villain
• Fairy tale villain associated with the ends of 20-, 27- and 49-Across
• Literary villain whose modus operandi is described by the ends of 20-, 34-, and 41-Across
• Fairy-tale villain
• James Patterson book
• Villain in the story named by the starts of 17-, 25-, 47- and 57-Across