malignant

Harmful, malevolent, injurious.

malignant temper; malignant revenge; malignant infection

[…]while, I fear, there will be some white ones, unable to forget that, with malignant heart, and deceitful speech, they have strove to hinder it.

Tending to produce death; threatening a fatal issue.

malignant diphtheria

a malignant tumor

A deviant; a person who is hostile or destructive to society.

As devout Stephen was carried to his burial by devout men, so is it just and equal that malignants should carry malignants […]

A malignant in a position of real power immediately becomes a tyrant.

A person who fought for Charles I in the English Civil War.