Place the chicken breasts in the slow cooker. Add the chicken broth, diced tomatoes, black beans, corn, onion, and garlic.
Stir in the cumin, chili powder, salt, and black pepper. Cover and cook on low for 6 to 7 hours.
Remove the chicken breasts and shred them with two forks. Return the shredded chicken to the slow cooker.
Stir in the lime juice. Let the soup cook for 10 more minutes on low.
Ladle the soup into bowls. Top each serving with avocado slices, tortilla strips, and chopped cilantro. Serve with lime wedges on the side.