Combine buttermilk and hot sauce in a bowl. Add chicken, cover, and refrigerate for at least 4 hours or overnight to tenderize and flavor.
Mix flour, cornstarch, paprika, garlic powder, onion powder, cayenne, salt, and pepper in a bowl for a crispy, flavorful crust.
Remove chicken from marinade, let excess drip off, and coat thoroughly in the flour mix. For extra crunch, dip back briefly in buttermilk, then coat again. Shake off excess.
Heat vegetable oil 2 inches deep in a skillet or Dutch oven to 350°F (175°C). Maintain temperature to avoid burning or greasiness.
Fry chicken in batches without crowding for 12–15 minutes, turning occasionally, until golden brown and 165°F (74°C) internally.
Place chicken on paper towels or a rack to drain oil. Let rest a few minutes to keep crust crisp and meat juicy.