In a large pot, heat the olive oil over medium heat. Add the diced onion and red bell pepper, sautéing until soft, about 5 minutes. Stir in the minced garlic and cook for another minute until fragrant.
Sprinkle the taco seasoning over the sautéed vegetables and stir to combine.
Add the chicken breasts, black beans, kidney beans, corn, diced tomatoes with green chilies, and chicken broth to the pot. Stir everything together.
Bring the mixture to a gentle boil, then reduce heat and cover the pot. Let it simmer for about 20-25 minutes, or until the chicken is cooked through.
Remove the chicken from the pot and use two forks to shred it. Return the shredded chicken to the pot and stir everything well.
Taste the soup and season with salt and pepper as needed. If you like it spicier, add more taco seasoning or a pinch of crushed red pepper flakes.
Ladle the soup into bowls and allow everyone to add their favorite toppings like avocado slices, shredded cheese, sour cream, or fresh cilantro. Serve with tortilla chips on the side for added crunch.
Notes
Feel free to customize toppings based on preference.