In a large pot or Dutch oven, heat olive oil over medium heat. Sauté chopped onion for 5-7 minutes until softened, then add minced garlic and chopped bell peppers. Cook for an additional 3-5 minutes.
Add cubed chicken breasts to the pot and brown on all sides for about 5-7 minutes.
Stir in chili powder, cumin, smoked paprika, cayenne pepper (if using), oregano, salt, and black pepper; cook for 1 minute.
Pour in chicken broth, black beans, kidney beans, corn, diced tomatoes (with juices), and tomato sauce; stir well.
Bring to a boil, then reduce heat to low and cover. Simmer for at least 20 minutes.
Shred the chicken directly in the pot after ensuring it's cooked through.