Chop the onion, green bell peppers, and red bell peppers into uniform pieces. Mince the garlic cloves.

In a large, heavy-bottomed pot or Dutch oven, heat the olive oil over medium-high heat. Add the ground beef and cook, breaking it up with a spoon, until it is browned. Drain off any excess grease after browning.

Once the beef is browned and drained, add the chopped onion and bell peppers to the pot. Sauté over medium heat for about 5-7 minutes, or until the vegetables have softened and the onions are translucent.

Stir in the minced garlic, chili powder, cumin, smoked paprika, oregano, cayenne pepper (if using), salt, and black pepper. Cook for another minute, stirring constantly, until fragrant.

Pour in the crushed tomatoes, tomato sauce, and diced tomatoes (undrained) into the pot. Add the rinsed and drained kidney beans, black beans, and pinto beans. Stir well to combine all the ingredients.

Pour in the beef broth and bring the chili to a simmer. Once simmering, reduce the heat to low, cover the pot, and let it simmer for at least 1 hour. Stir occasionally.

After simmering, taste the chili and adjust the seasoning as needed. Add the optional brown sugar if you find the chili too acidic.

Ladle the chili into bowls and garnish with your favorite toppings.