Came across this story a while back:
and
https://www.nytimes.com/2018/08/12/world/middleeast/Iraqi-spy-isis.html
This gave me goosebumps. Imagine being surrounded by men who'd kill you without hesitation if your identity were known. He was later discovered and killed, but not before he had foiled dozens of attacks.
Other stories on the guy:
https://www.hstoday.us/subject-matter-areas/terrorism-study/the-isis-spy-who-saved-baghdad-from-30-bombing-missions/
https://alshahidwitness.com/Iraqi-spy-infiltrated-daesh/