Prepare the Batter. In a large bowl, whisk together flour, cornstarch, baking powder, garlic powder, paprika, salt, and pepper. Slowly pour in the beer, whisking continuously until you achieve a smooth, lump-free batter. Let it rest for 10 minutes to allow flavors to meld.
Coat the Fish. Pat the fish fillets dry with a paper towel to remove excess moisture. Lightly coat the fish with a dusting of flour before dipping them into the batter to help it adhere better.
Fry to Crispy Perfection. Heat vegetable oil in a deep skillet or fryer to 375°F. Carefully place battered fish into the hot oil, frying in batches to avoid overcrowding. Fry for 3-4 minutes per side or until the fish is golden brown and crispy. Transfer to a wire rack or paper towels to drain excess oil.
Garnish and Serve. Serve immediately with lemon wedges and your favorite dipping sauces.