Place the slow cooker on a stable surface and prepare your ingredients. Season the chicken breasts lightly with salt and pepper, then set them in the bottom of the crockpot.
Chop the onion, garlic, and bell pepper into small, even pieces to ensure they soften beautifully during cooking. Add these vegetables directly on top of the chicken.
Pour in the diced tomatoes with their juice and the chicken broth. Sprinkle in the cumin and chili powder, then give everything a gentle stir to combine the flavors.
Cover the slow cooker with its lid and cook on low for 6 to 8 hours. The house will fill with a fragrant aroma of spices and simmered vegetables.
Once the cooking time is up, open the lid and check if the chicken is tender enough to shred easily with tongs or forks. If so, shred the chicken directly in the pot, letting it soak up all those savory flavors.
Add the corn kernels and chopped cilantro to the soup, then stir gently to combine. Cover again and let sit for 10 minutes so the flavors meld and the corn heats through.
Use a ladle to serve the hot soup into bowls. Garnish with additional cilantro, slices of avocado, shredded cheese, or tortilla chips if desired for extra crunch and flavor.