In a large pot or Dutch oven, heat the vegetable oil over medium heat. Add the chopped onion and bell pepper, and sauté for about 5 minutes until softened.
Add the minced garlic and ground beef to the pot. Cook until the beef is browned, breaking it apart with a wooden spoon, about 5-7 minutes.
Stir in the chili powder, cumin, paprika, salt, and black pepper. Mix well and cook for another 1-2 minutes to toast the spices.
Add the diced tomatoes (with juices), drained kidney beans, drained black beans, and beef broth. Stir everything together until combined.
Bring the mixture to a simmer. Reduce heat to low and cover the pot. Let it simmer for about 45 minutes to 1 hour, stirring occasionally.
Taste the chili and adjust seasoning if necessary. If it seems too thick, you can add a little more beef broth or water.
Serve the chili hot in bowls. Top with shredded cheese, sour cream, chopped green onions, or cilantro if desired.