1. In a 4 quart Dutch oven over medium heat, cook ground beef, onion, green pepper, and garlic until meat is browned and vegetables are tender, stirring occasionally to break up meat.
2. Pour off fat, if any.
3. Stir in soup, kidney beans with their liquid, chili powder, and vinegar. Heat to boiling. Reduce heat to low, simmer, uncovered for 30 minutes, stirring occasionally.
4. Ladle into bowls; top with sour cream and sliced green onions.