Poltergeists

Poltergeists are perhaps the least objectionable of the non-beings. Mrs. Rowling tells us that they tend to appear wherever "young people, especially adolescents, are living."¹ She has further stated that they are indestructible² with implied confirmation in that attempts to remove Peeves have failed.³

That being said, these seem to be more or less morally neutral. They will plague anyone for any or no reason, and they seem to have some concept of affection (see their relationship with the Weasley twins for example).