Possible Clues:

• Villain
• Heavy
• Billie Eilish hit song
• Hit song by the 1-Across winner whose name is spelled out by the final three letters of 21-, 25-, 47- and 52-Across
• Villain in an old movie
• Action film foil
• Villain that might create problem in camp
• Villain of a piece
• The Joker in Batman movies, e.g.
• One to root against