Heat the oil in a large dutch oven or stock pot over medium-high heat. Once the oil is glistening, add the onion, bell peppers, and sweet potatoes and cook, stirring, until the onion begins to soften, 5 minutes. Add the garlic and cook, stirring, until fragrant, about 2 minutes more.
Stir in the black beans, kidney beans, pinto beans, tomatoes, enchilada sauce, chili powder, cumin, bay leaves, garlic powder, onion powder and salt until combined. Add enough water to cover the beans, about 1 to 2 cups.
Increase the heat to high and bring to a boil, then reduce the heat to low and simmer, stirring occasionally, for about 1 hour, or until the potatoes are tender and the chili has thickened.
Divide among bowls and serve topped with cheddar cheese, sour cream, avocado, cilantro and green onions, if using.