Heat olive oil in a large pot over medium heat.
Add onion and garlic.
Cook until soft and fragrant, about 3–4 minutes.
Add ground beef.
Cook until browned, breaking it up with a spoon. Drain excess fat if needed.
Stir in red bell pepper and tomato paste. Cook 2–3 minutes to deepen flavors.
Add chili powder, cumin, smoked paprika, cayenne, salt, and pepper. Stir to coat evenly.
Pour in diced tomatoes and broth. Stir in brown sugar if using.
Bring to a boil, then reduce heat to low. Cover and simmer for 10 minutes.
Add the beans and continue cooking, stirring occasionally, for about 30 minutes, until the chili thickens and flavors meld.
Taste and adjust seasoning. Serve hot with your favorite toppings.