In a large pot or Dutch oven, heat olive oil over medium heat. Add the diced onion and sauté for about 5 minutes, until translucent.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the chicken breasts to the pot along with cumin, oregano, chili powder, and salt and pepper. Cook for about 5 minutes, turning the chicken until it browns slightly.
Pour in the canned green chilies and chicken broth. Bring the mixture to a boil, then reduce the heat and let it simmer for 20 minutes, or until the chicken is cooked through.
Remove the chicken from the pot and shred it using two forks. Return the shredded chicken back to the pot.
Stir in the black beans, corn, diced tomatoes, and lime juice. Cook for an additional 5-10 minutes until heated through.
Adjust seasoning with salt and pepper if needed. Serve hot, garnished with chopped cilantro and avocado if desired.