Layer the base: Add onion, garlic, and bell pepper to the slow cooker. Pour in the black beans, corn, fire-roasted tomatoes, and the tomatoes with green chilies.
Season it well: Sprinkle in chili powder, cumin, smoked paprika, oregano, salt, and pepper. Stir to coat the veggies and beans with the spices.
Add chicken and broth: Nestle the chicken breasts (or thighs) into the mixture.
Pour in the chicken broth so everything is mostly submerged.
Cook low and slow: Cover and cook on Low for 6–7 hours or High for 3–4 hours, until the chicken is tender and easily shreds.
Shred the chicken: Remove the chicken to a cutting board and shred with two forks. Return the chicken to the slow cooker and stir.
Brighten the flavors: Stir in the lime juice. Taste and adjust salt, pepper, or chili powder as needed.
Serve and top: Ladle into bowls and finish with tortilla strips, cilantro, avocado, cheese, or a dollop of sour cream.
Add lime wedges on the side.