1. In a large pot, heat some oil over medium heat. Add the chopped onion and minced garlic, and sauté until the onion is translucent.
2. Add the chicken breast to the pot and cook until browned on all sides.
3. Pour in the chicken broth, diced tomatoes, corn, and black beans. Stir to combine.
4. Add the cumin, chili powder, salt, and black pepper. Bring the soup to a boil, then reduce the heat and let it simmer for about 20 minutes, or until the chicken is cooked through.
5. Remove the chicken breast from the pot, shred it with two forks, and return it to the soup. Stir well and let it simmer for another 5 minutes.
6. Serve hot, garnished with fresh cilantro, avocado slices, and a squeeze of lime if desired.