In a large skillet over medium-high heat, brown the ground beef with the diced onion until the meat is no longer pink and the onion is softened, about 8-10 minutes. Add the garlic and cook for another minute until fragrant. Drain any excess fat.
Transfer the beef mixture to your slow cooker.
Add the beer, kidney beans, crushed tomatoes, tomato paste, chili powder, cumin, smoked paprika, salt, and pepper. Stir everything together until well combined.
Cover and cook on LOW for 6-8 hours or on HIGH for 3-4 hours, stirring occasionally if you're around.
Taste and adjust seasonings as needed. Serve hot with your favorite toppings like shredded cheese, sour cream, and chopped green onions.