Heat olive oil in a large pot over medium heat.
Add chopped onion and sauté until translucent.
Stir in minced garlic and diced bell pepper; cook for another 2 minutes.
Add the canned tomatoes, including their juices, to the pot.
Pour in the chicken broth and bring to a boil.
Reduce heat and add shredded chicken, black beans, cumin, and chili powder.
Season with salt and pepper; simmer for 20 minutes.
Meanwhile, in a separate pan, fry tortilla strips until crispy.
Serve the soup hot, topped with crispy tortilla strips.
Garnish with fresh cilantro, lime wedges, and avocado slices.