In a large skillet over medium-high heat, brown the ground beef, breaking it up as it cooks. Drain excess fat and transfer to slow cooker.
Add all three types of beans, diced tomatoes, tomato paste, onion, bell pepper, and garlic to the slow cooker.
Pour in the beef broth and add chili powder, cumin, paprika, salt, black pepper, and cayenne if using. Stir everything together until well combined.
Cover and cook on low for 6-7 hours or on high for 3-4 hours, stirring occasionally if possible.
Taste and adjust seasonings as needed. Serve hot with your favorite chili toppings like shredded cheddar cheese, sour cream, chopped cilantro, and jalapeño slices.