Cook and stir the beef, onion, and bell pepper in a large pot over medium heat until the beef is brown and onion and pepper are tender, about 10 minutes. Drain grease from beef.
Stir in beans, tomatoes, tomato sauce, jalapenos (if using), chili powder, red pepper flakes, black pepper, salt, and garlic powder. Bring mixture to a slow boil; cover and reduce heat. Simmer chili at least 30 minutes, stirring occasionally so that it does not stick. This chili can be simmered for several hours; the longer you simmer, the more flavor you will get.