In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes, or until softened.
Stir in the minced garlic, bell pepper, cumin, chili powder, smoked paprika, and cayenne pepper (if using). Cook for another 2-3 minutes until fragrant.
Pour in the chicken broth and add the diced tomatoes, black beans, corn, and shredded chicken. Bring the mixture to a simmer and cook for 10-15 minutes to allow the flavors to meld.
Reduce the heat to low and stir in the heavy cream. Season with salt and pepper to taste. Heat through for another 5 minutes, but do not boil.
Serve the soup hot, topped with crushed tortilla chips, shredded cheddar cheese, chopped cilantro, and diced avocado. Squeeze fresh lime juice over each bowl before serving.