Place the chicken breasts in the bottom of the slow cooker. Add the chicken broth, diced tomatoes with green chilies, black beans, corn, onion, and garlic.
Sprinkle in the chili powder, cumin, salt, and black pepper. Stir gently to combine everything around the chicken.
Cover and cook on low for 6 to 7 hours until the chicken is fully cooked and easy to shred.
Remove the chicken, shred it with two forks, and return it to the slow cooker. Stir to mix it back into the soup.
Ladle the soup into bowls and top each serving with diced avocado and tortilla strips.