Heat a large pot or Dutch oven over medium heat. Add the ground beef and diced onion, then cook for 6 to 8 minutes while breaking the beef into small pieces, until the meat is browned and the onion is softened.

Drain excess fat from the pot if necessary. Stir in the taco seasoning and ranch dressing seasoning mix until the beef and onion are evenly coated and fragrant.

Add the undrained pinto beans, drained and rinsed black beans, drained and rinsed kidney beans, undrained corn, diced tomatoes, tomatoes with green chiles, tomato sauce, and 1 cup of broth or water. Stir thoroughly to combine.

Bring the soup to a boil over medium-high heat. Once bubbling, reduce the heat to low, partially cover the pot, and simmer for 20 to 30 minutes, stirring occasionally.

Check the consistency during cooking and add the remaining broth or water if the soup becomes thicker than you prefer. Taste near the end and adjust the seasoning as needed.

Ladle the hot soup into bowls and finish with your preferred toppings. Serve with shredded cheese, sour cream or plain Greek yogurt, green onions, cilantro, avocado, tortilla chips, lime wedges, or sliced jalapeños.