>>48527983>Being spiteful and banefulThe devils in the details. You have to remember why they might be, and in many cases it's because dark type Pokemon are simply misunderstood rather than being outright malicious. I'd say a good chunk are "mean" mainly because their environment meant having to adapt to that lifestyle. Think of Darkrai for example, which is commonly described to mainly put people into deep nightmares as a self defense mechanism.
It may sound cruel, but for Darkrai or other dark types it's a matter of survival. The idea of being spiteful/baneful and leading to angry unrestful spirits is also common in Japanese myth or media.
I know the "dark is evil" thing in Japanese, but I think that refers more to "tactics" which for their society is also a measure of one's personal honor/nature. Doing anything to get ahead in life would naturally be seen as evil, as opposed to how the west rewards such actions.