In a skillet over the stove top on high heat, cook and brown hamburger with minced garlic and diced onions, until the meat is no longer pink. Drain the fat, if there is any.
Add the hamburger mixture to the slow cooker.
Add chili beans, light and dark red kidney beans, Rotel, tomato sauce, beef broth, cumin, chili powder, salt, sugar, black pepper, oregano, basil, and green chilis to the slow cooker and stir until well combined.
Cover with the lid and cook on low for at least 8 hours or on high for 4 hours.
Serve over baked potatoes or in a bowl with your favorite toppings (sour cream, cheese, diced green onions, crushed tortilla chips, etc.)_