Prepare chicken: Place chicken in slow cooker.
Add vegetables and beans: Add diced tomatoes, green chiles, corn, black beans, and chopped onion.
Season: Add garlic, chili powder, cumin, smoked paprika, oregano, salt, and pepper.
Add broth: Pour chicken broth over all ingredients. Stir gently to combine.
Slow cook: Cover and cook on low for 4–5 hours or high for 2–3 hours, until chicken is fully cooked and tender.
Shred chicken: Remove chicken from slow cooker, shred with two forks, and return to soup. Stir to combine.
Serve: Ladle soup into bowls. Top with diced avocado, tortilla strips, lime wedges, fresh cilantro, and optional shredded cheese or sour cream.