Heat the olive oil in a large pot over medium heat. Add the diced onion and sauté for 3-4 minutes until softened.
Stir in the minced garlic and cook for another minute until fragrant.
Add the diced bell pepper, sliced carrots, and sliced celery. Continue to cook for about 5 minutes, stirring occasionally, until the vegetables begin to soften.
Mix in the ground cumin and chili powder, stirring to coat the vegetables evenly.
Pour in the chicken broth, followed by the shredded chicken, diced tomatoes, black beans, and corn. Bring the mixture to a boil.
Reduce the heat to a simmer and let it cook for 20-25 minutes, allowing the flavors to meld and the vegetables to cook through.
Taste the soup and season with salt, pepper, and lime juice as needed.
Serve hot, garnished with fresh cilantro and avocado slices, if desired.