Brown hamburger meat and onions in a large skillet, drain. Then transfer meat and onions to a large crockpot. Add corn, tomatoes, green chiles, black olives, green olives, taco seasoning and ranch dressing mix and cook on low for 6 to 8 hours or you can cook on stove on low for an hour or so. To serve, put corn chips in a bowl and ladle soup over them...add desired amount of shredded cheddar cheese and sour cream. If you wish, you can top with green onions.