In PASV01, Pikachu was used to battle against Nemona's Pawmi during the Uva Academy opening ceremonies. The battle ended inconclusively, because after both had used Terastal to battle, Violet suddenly arrived at the battle arena, causing all the attention to be focused on him.
In PASV06, Pikachu was the last Pokémon used in Scarlet's battle against Katy where it battled the Gym Leader's Terastalized Teddiursa, and after she herself used her Terastal power, Pikachu was able to beat Teddiursa and thus give victory to her Trainer.
In PASV12, Pikachu was used as Scarlet's last resort against Iono.