Warm the oil in a large pot over medium heat.
Sauté the onion and bell pepper until softened, about 5 minutes.
Stir in the garlic and tomato paste; cook 1 minute until fragrant.
Add the ground beef. Cook, breaking it up, until browned. Drain excess fat if needed.
Sprinkle in chili powder, cumin, paprika, oregano, cayenne, salt, and pepper. Toast 30 seconds, stirring.
Pour in diced tomatoes, tomato sauce, and broth. Scrape the pot to release browned bits.
Stir in the kidney and pinto beans. Add brown sugar if using, then bring to a gentle simmer.
Reduce heat and simmer uncovered 20–25 minutes, stirring occasionally, until thickened. Adjust salt to taste.