In a large pot or Dutch oven, heat a drizzle of oil over medium heat. Add the ground beef and chopped onion. Cook until the beef is browned and the onion is translucent, about 5-7 minutes. Use a wooden spoon to break up the meat as it cooks.
Once the beef is cooked, stir in the kidney beans, black beans, corn kernels, diced tomatoes, and tomato sauce. Mix well to combine all the ingredients.
Sprinkle the taco seasoning over the soup mixture. Stir to ensure that the seasoning is evenly distributed throughout the soup.
Bring the soup to a gentle boil, then reduce the heat to low. Let it simmer for about 15 minutes, allowing the flavors to meld together. Stir occasionally to prevent sticking.
Ladle the soup into bowls and top with shredded cheddar cheese, a dollop of sour cream, diced tomatoes, avocado slices, and a handful of corn chips. Finish with a squeeze of lime and a sprinkle of fresh cilantro for an extra burst of flavor.
