Place the chicken breasts in the bottom of the slow cooker and sprinkle with salt, pepper, and chili powder.
Add the diced onion, black beans, and frozen corn on top of the chicken.
Pour the enchilada sauce evenly over the ingredients.
Scatter half of the torn tortillas and half of the shredded cheese over the sauce layer.
Repeat the layers with the remaining tortillas and cheese.
Cover and cook on low for 6 hours until the chicken reaches an internal temperature of 165°F and shreds easily.
Shred the chicken directly in the slow cooker and stir everything together so the sauce coats all the ingredients before serving.