1. Heat the olive oil in a large pot or Dutch oven over medium heat. Add the chopped onion and green bell pepper and cook until softened, about 4 to 5 minutes. Stir in the garlic and cook for 30 seconds.

2. Add the ground beef and cook until browned, breaking it up with a spoon as it cooks. Drain excess grease if needed.

3. Stir in the diced tomatoes, tomato paste, and beef broth until well combined.

4. Add the chili powder, cumin, smoked paprika, oregano, salt, black pepper, and crushed red pepper flakes. Stir well to coat the meat and vegetables.

5. Bring the chili to a gentle simmer, then reduce the heat to low. Let it cook uncovered for 25 to 30 minutes, stirring occasionally, until thickened.

6. Taste and adjust seasoning if needed.

7. Serve hot with shredded cheddar cheese, sour cream, sliced avocado, and chopped green onions.