01 - Heat a large skillet over medium-high heat. Add the ground beef and cook, breaking it apart with a spoon, until browned and no longer pink. Drain excess fat and set aside.
02 - Add the diced onion, red and green bell peppers, and garlic to the skillet. Sauté for 2–3 minutes until slightly softened and fragrant.
03 - Transfer the beef and vegetable mixture to a 5–6 quart slow cooker.
04 - Add the kidney beans, black beans, diced tomatoes with their juices, tomato paste, beef broth, chili powder, cumin, smoked paprika, oregano, salt, black pepper, and cayenne pepper. Stir thoroughly to combine all ingredients.
05 - Cover and cook on low heat for 6–7 hours, or on high heat for 3–4 hours, until flavors are fully developed and chili has thickened.
06 - Taste the chili and adjust salt, pepper, or cayenne as desired. Serve hot with shredded cheddar cheese, sour cream, chopped green onions, or fresh cilantro if desired.