Start by placing the boneless, skinless chicken breasts at the bottom of the slow cooker.
In a mixing bowl, combine the drained black beans, kidney beans, corn, diced tomatoes (with juices), diced onion, and minced garlic. Stir well.
Pour the bean and tomato mixture over the chicken in the slow cooker.
In another bowl, mix the chicken broth, chili powder, cumin, paprika, onion powder, salt, and black pepper. Pour this seasoning mixture over the contents in the slow cooker.
Cover the slow cooker with its lid and cook on low for 6-8 hours or on high for 4-6 hours, until the chicken is tender and fully cooked.
Once done, remove the chicken breasts and shred them with two forks. Return the shredded chicken to the soup and stir everything together to combine.
Taste and adjust the seasoning if necessary, adding more salt or spices as desired.
Serve the soup hot in bowls, adding your choice of optional toppings like shredded cheese, avocado slices, cilantro, sour cream, and lime wedges for added flavor and texture.
Notes
Feel free to customize with your favorite toppings.