General:
* Reveals
* Leaked information
* Plot twists
* Giveaways
* Previews (used sarcastically)
* Blew the ending
* Ruined the surprise
* Secret-busters
More specific:
* Plot leaks (for movies, TV shows, etc.)
* Game spoilers (for video games)
* Book spoilers (for novels)
* Ending spoilers (for stories in general)
* Twist endings (for surprises within a story)
Figurative/Informal:
* Ruined it
* Bummer (if something is spoiled)
* Let the cat out of the bag (to reveal a secret)
The best synonym for "spoilers" will depend on the specific situation and what you want to convey.