In a skillet over medium heat, brown the ground beef until fully cooked. Drain excess fat and add the beef to the crockpot.
Add the diced onion, minced garlic, and diced bell pepper to the crockpot with the ground beef.
Pour in the kidney beans, black beans, and diced tomatoes (with juice).
Sprinkle in the chili powder, cumin, paprika, salt, and black pepper.
Pour the beef broth over the mixture, giving it a gentle stir to combine all ingredients.
Cover the crockpot and cook on low for 6 hours, or high for 3 hours.
Serve hot, topped with shredded cheese, sour cream, and chopped green onions if desired.