Poplar

Information

Opal is the Gym Leader of Ballonlea's Gym, known officially as Ballonlea Stadium. She specializes in Fairy-type Pokémon. She gives the Fairy Badge to Trainers who defeat her. During the events of Pokémon Sword and Shield, she chooses Bede as her successor and passes her Gym Leader title on to him.

(Source: Bulbapedia)