Add the oil, onion, celery, and carrots to a large soup pot over medium-high heat. Sauté for 5-7 minutes (light browning adds more flavor).
Add the diced tomatoes, chicken broth, corn, black beans, garlic powder, cumin, chili powder, cayenne pepper, and chicken breasts to the pot. Give it a stir, then increase the heat to high and bring it to a boil. Once boiling, reduce the heat, cover the pot with the lid slightly ajar, and simmer for 20 minutes or until the chicken is cooked through.
Take the chicken out of the pot and cut it up/shred it, then add it back to the pot.
Season the soup with salt & pepper as needed. I recommend adding a good squeeze of fresh lime juice and a handful of chopped cilantro to the soup prior to serving, but that step is optional. Serve and top each bowl as desired with any extra garnishes (tortilla strips, sour cream, cheese, etc.).