Mix the ground beef, eggs, bread crumbs, onion, milk, salt, and black pepper together in a large mixing bowl until evenly combined. Form the mixture into 12 large meatballs. Arrange the meatballs into a 9x13-inch baking dish.
Stir the ketchup, tomato sauce, water, brown sugar, white sugar, Worcestershire sauce, Italian seasoning, and chili powder together in a saucepan over medium heat; cook and stir until well combined and hot, about 5 minutes. Pour the tomato sauce mixture over the meatballs in the baking dish. Turn the meatballs to coat in the sauce.
Bake in the preheated oven until the meatballs are cooked through and no longer pink in the center, 60 to 90 minutes.