Grate the peeled potatoes into a large bowl. Place the grated potatoes in a clean kitchen towel and squeeze firmly to remove excess moisture. Return the drained potatoes to the bowl. Add sweet corn, egg, flour, green onions, garlic powder, salt, and black pepper. Mix until well combined and the mixture holds together when pressed. Heat 2 tablespoons of vegetable oil in a skillet over medium heat. Scoop about 2 tablespoons of mixture and flatten gently into a 1/2-inch thick patty. Place into the hot skillet without overcrowding. Cook for 3–4 minutes per side until golden brown and crisp. Add additional oil as needed for remaining batches. Transfer cooked fritters to a paper towel-lined plate before serving.