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