In a large skillet over medium heat, cook the ground beef until browned, breaking it up with a spoon as it cooks, about 6-8 minutes.
Add the diced onion and minced garlic to the skillet with the beef and cook until the onion is soft and translucent, about 3-4 minutes.
Drain any excess fat from the skillet.
In a large pot, combine the cooked ground beef mixture, black beans, kidney beans, corn, diced tomatoes with green chilies, diced tomatoes with mild green chilies, tomato sauce, and beef broth.
Stir in the taco seasoning mix, ground cumin, and chili powder until well combined.
Bring the soup to a boil over medium-high heat, then reduce the heat to low and let it simmer uncovered for 20 minutes, stirring occasionally.
Season with salt and black pepper to taste.
Allow the soup to cool completely before transferring it into freezer-safe containers or bags.
Label and freeze for up to 3 months.
To reheat, thaw the soup overnight in the refrigerator and warm it on the stove over medium heat until heated through.