Heat the olive oil in a large pot over medium heat. Add the onion and garlic and cook for 3 minutes until the onion softens.
Pour in the chicken broth and diced tomatoes. Stir in the shredded chicken, black beans, corn, cumin, chili powder, and salt.
Bring the soup to a simmer and cook for 15 minutes, stirring occasionally.
Remove the pot from the heat and stir in the lime juice.
While the soup simmers, place the tortilla strips on a baking sheet and bake at 400°F for 5 to 7 minutes until crisp.
Ladle the soup into bowls and top each serving with tortilla strips, avocado slices, and chopped cilantro.