Characterized by intense ill will or spite
Extremely destructive or harmful
Note that the malignant cells are invading and destroying the muscle fibres of the heart.
In this way they give rise to a malignant new growth.
A malignant attitude will turn others away from friendship
Amber hoped that her son did not show his malignant side at his new school.
Malaria is widely prevalent, and in some years, after a wet spring, assumes a malignant character.