Malignant
/məˈlɪɡnənt/
noun
A deviant; a person who is hostile or destructive to society.
A person who fought for Charles I in the English Civil War.
adjective
Harmful, malevolent, injurious.
“malignant temper; malignant revenge; malignant infection”
Tending to produce death; threatening a fatal issue.
“a malignant tumor”