I taught all my dragons either a steel move or a generally strong one capable of taking advantage against some fairy's secondary type (eg I sicced my salamence on a gardevoir and used steel wing to one shot it) or u turn



with dragons you basically got to teach it a good dragon move and an emergency move for fairies. Or make them tough enough to survive a hit. Even hydreigon with the right set up can take a 4x and strike back.