There's nothing more shocking than learning a villain has been in plain sight all along. The most famous example of the 2020s is Subject 001 on Stranger Things, whom Eleven learned was the orderly that turned into Vecna. Fans were surprised that the first ever subject turned out to be Hawkins' worst nightmare. However, there have been wilder instances of other TV villains showing their true colors.
Source：https://www.cbr.com/better-secret-tv-villains-than-stranger-things-001/
