Pat chicken dry and season with ½ teaspoon salt and ½ teaspoon pepper. Heat 2 tablespoons oil over medium-high heat in a large Dutch oven/soup pot. Add chicken and sear until golden, about 2 minutes per side. Remove to a plate but leave drippings. Add onions, sweet potatoes, and bell peppers and cook, stirring occasionally, until the onions are softened, about 5 to 7 minutes. Stir in garlic, and all seasonings, and cook, for 1 minute.
Add chicken back to pot followed by the rest of the ingredients (though chicken bouillon).
Bring to a boil, reduce heat and simmer until the chicken is tender, about 12-15 minutes, stirring occasionally so the bottom doesn’t burn. Remove the chicken to a plate and continue to simmer the soup until the sweet potatoes are tender, about 5 minutes. In the meantime, shred the chicken with two forks.
Add shredded chicken back to the pot and cook on low for a couple minutes to soak up the flavors. Taste and season with salt, pepper and/or cayenne pepper to taste (I add 1/4-1/2 teaspoon salt).
Ladle chili into bowls and top with desired toppings such as sour cream, shredded cheese, tortilla chips and green onion.