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 minced garlic to the skillet. Sauté for 2–3 minutes until vegetables are slightly softened and fragrant.
03 - Transfer the beef mixture to a 5–6 quart slow cooker. Add the 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 incorporate all ingredients.
04 - Cover and cook on low heat for 6–7 hours, or on high heat for 3–4 hours, until flavors have melded and chili is thickened.
05 - Taste the chili and adjust salt, pepper, or cayenne as desired. Serve hot, topped with shredded cheddar cheese, sour cream, green onions, or fresh cilantro if preferred.