Heat a large skillet over medium-high heat. Add the ground beef and diced onion.
Cook for 6–8 minutes, breaking up the beef, until browned and the onion is softened. Drain excess grease.
Add the minced garlic and chopped jalapeño. Cook for another 30–60 seconds.
Transfer the beef mixture to a 6-quart slow cooker.
Add the diced bell pepper, kidney beans, black beans, pinto beans, diced tomatoes, tomato sauce, tomato paste, and beef broth.
Add the chili powder, cumin, smoked paprika, oregano, cayenne, black pepper, and salt.
Stir thoroughly until all ingredients are combined.
Cover and cook on LOW for 6–8 hours or HIGH for 3–4 hours.
Stir the chili before serving and taste. Adjust the salt or heat as desired.
Let the chili rest for about 10 minutes before serving with your favorite toppings.