1. In a large skillet, cook the ground beef over medium heat until browned. Drain any excess fat.
2. Add the chopped onion, green bell pepper, and minced garlic to the skillet. Cook until softened, about 5 minutes.
3. Transfer the beef and vegetable mixture to the slow cooker.
4. Add the diced tomatoes, tomato sauce, kidney beans, black beans, chili powder, ground cumin, paprika, salt, and black pepper to the slow cooker. Stir to combine.
5. Cover and cook on low for 8 hours or on high for 4 hours.
6. Serve hot, garnished with your favorite toppings like shredded cheese, sour cream, or chopped green onions.