In large saucepan over medium heat, cook ground beef and onion until meat is browned and onion is tender, 5-7 minutes.
Stir in tomato sauce, kidney beans, stewed tomatoes with juices, diced tomatoes with green chilies and cubed sweet potato. Add water to reach desired consistency.
Season with chili powder and garlic powder. Add salt and pepper, to taste.
Bring to boil then reduce heat to low. Cover and simmer 15 minutes.
Serve with sour cream and sliced avocado, if desired.