Badsmella in Yo-kai Watch 2

When Nate/Katie is in the past to help complete the Yo-kai Watch Model Zero, Badsmella first appeared when the player went to get the Watch part located in the Ironworks, inspiriting the workers to be lazy by using the black haze she had created. She then played a game of hide-and-seek with the player, and after being cornered 3 times (with two times being innocent Yo-kai hiding in the factory), Badsmella fights the player, but is defeated, and was turned into a regular Smogmella.

Otherwise, Badsmella is exclusive to Psychic Specters. You can befriend Badsmella by fusing Smogmella with an Essence of Evil. The Essence of Evil is given as rewards for completing the Wicked Executive Yo-kai quests.

Version exclusive: Yo-kai Watch 2 Psychic Specters.