In a large pot, heat a tablespoon of oil over medium heat.
Add the chopped onion and bell pepper; sauté until soft.
Stir in the minced garlic and cook for another minute.
Add the diced tomatoes, corn, chicken, and spices.
Pour in the chicken broth and bring to a boil.
Reduce heat and let it simmer for 20 minutes.
Season with salt and pepper to taste.
Remove from heat and stir in fresh cilantro.
Serve hot, garnished with avocado slices.
Enjoy your delicious Mexican chicken soup!