In a large pot or Dutch oven, heat a bit of oil over medium heat. Add the ground beef and cook, breaking it up into small pieces, until browned and fully cooked, about 5-7 minutes. Drain any excess fat from the beef.

Add the diced onion, bell pepper, and minced garlic to the pot with the ground beef. Sauté for 2-3 minutes, stirring occasionally, until the vegetables have softened.

Stir in the chili powder, cumin, paprika, cayenne pepper (if using), salt, and black pepper. Let the spices cook for 1 minute to release their flavors.

Add the kidney beans, pinto beans, diced tomatoes, tomato paste, and beef broth to the pot. Stir everything to combine well. Add the sugar to balance the acidity from the tomatoes.

Bring the mixture to a boil, then reduce the heat to low and cover the pot. Let it simmer for 30-45 minutes, stirring occasionally. This will allow the flavors to meld together and the chili to thicken. If the chili gets too thick, add a little water or more broth to reach your desired consistency.

Season with salt and pepper to taste. Serve hot.