Sauté Aromatics: In a large Dutch oven or stockpot, heat the olive oil over medium-high heat. Add the ground beef and diced onion. Cook, breaking up the beef with a spoon, until the beef is browned and the onion is softened, about 5-7 minutes. Add the minced garlic and cook for 1 more minute until fragrant. Drain off any excess grease.
Add Seasonings: Sprinkle the taco seasoning and ranch seasoning over the meat mixture. Stir for 1 minute to coat everything and toast the spices.
Combine Ingredients: Pour in the beef broth to deglaze the pot, scraping up any browned bits. Add the black beans, kidney beans, corn, diced tomatoes (with their juices), and tomato sauce. Stir until everything is well combined.
Simmer: Bring the soup to a boil, then reduce the heat to low, cover, and let it simmer for 15-20 minutes to allow the flavors to meld together.
Serve: Ladle the hot soup into bowls and serve immediately, allowing everyone to top their portion with shredded cheese, a dollop of sour cream, avocado, cilantro, jalapeños, and crushed tortilla chips.