1. Lightly grease the inside of your slow cooker crock with cooking spray or a thin layer of oil to prevent sticking and make cleanup easier.

2. Place the boneless, skinless chicken breasts at the bottom of the prepared slow cooker. Evenly sprinkle the chopped onion and minced garlic over the chicken.

3. Pour in the rinsed and drained black beans, drained corn, crushed tomatoes, Rotel diced tomatoes with green chilies (undrained), and chicken broth. Gently stir to combine these ingredients around the chicken.

4. Sprinkle the taco seasoning, ground cumin, and chili powder over the mixture. Stir everything gently again, ensuring the spices are well distributed throughout the liquid. Season with a pinch of salt and freshly ground black pepper to your taste.

5. Cover the slow cooker with its lid. Cook on the LOW setting for 6-8 hours or on the HIGH setting for 4-6 hours. The chicken should be cooked through and easily shreddable with a fork.

6. Once the cooking time is complete and the chicken is tender, carefully remove the chicken breasts from the slow cooker. Place them on a cutting board and shred them using two forks. Return the shredded chicken to the soup and stir well to combine.

7. Give the soup a taste and adjust the seasonings if necessary. You might want to add a little more salt, pepper, or a dash more chili powder for extra warmth.

8. Ladle the warm soup into bowls and serve immediately with your favorite toppings.