>>50707536>Japanese name is literally あくタイプ (evil type)Localization made it more vague for some reason (maybe to avoid fueling the Satanic Panic). Dark-types are meant to be the assholes of the Pokemon world, but are seemingly more underhanded for survival's sake than outright evil. The reason Bug-type is super effective against Dark-type is because Kamen Rider is a crime fighting grasshopper cyborg.
The Pokemon least deserving of Dark-type is Absol, which is quite literally misunderstood in what it tries to do. But for some reason it's still Dark-type. Maybe its the way humans percieve these Pokemon that makes them "evil" and Dark-type Trainers understand that it may be more complicated than that. Or Dark-type Trainers are pretty shifty themselves, Grimsley certainly is.