Place chicken in the bottom of a slow cooker.
Sprinkle with chili powder, garlic powder, cumin, and onion powder.
Top evenly with salsa and green chile peppers.
Cook on Low until chicken breasts are very tender, 6 to 8 hours.
An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).
Shred chicken with 2 forks.
