Full of malign, deadly, or noxious influence; pernicious, destructive, noxious, injurious, mischievous, malignant. Morally.

Morally or socially injurious, noxious, or dangerous; grievous, ‘pestilent’. Obsolete.

Having an adverse effect on the state or condition of a person, society, etc.; mentally, emotionally, or morally damaging.