In a large pot or Dutch oven, heat over medium-high heat and add the ground beef. Cook until browned, breaking up the meat as it cooks, about 5-7 minutes. Drain any excess grease.

Add the diced onion and minced garlic to the pot. Cook until softened and fragrant, about 2-3 minutes.

Stir in the taco seasoning and cook for 1 minute to allow the flavors to bloom.

Add the black beans, kidney beans, corn, diced tomatoes, Rotel tomatoes, tomato sauce, diced green chilies, and beef broth to the pot. Stir well to combine.

Bring the soup to a boil, then reduce the heat to low. Cover and let simmer for 20-25 minutes, stirring occasionally.

Taste the soup and adjust the seasoning with salt and pepper, if needed.

Serve hot, topped with your favorite optional toppings like shredded cheese, sour cream, cilantro, avocado, tortilla chips, or a squeeze of lime.