malignant

adjective

1 a malignant growth in her left kidney:

cancerous, non-benign, metastatic.

▷antonyms benign.

2 a malignant disease:

virulent, infectious, invasive, uncontrollable, dangerous, harmful, pernicious;

deadly, fatal, life-threatening, lethal, terminal, incurable.

3 one of the most malignant glares she had ever seen:

spiteful, hostile, malevolent, malicious, malign, evil-intentioned, baleful, full of hate, vicious, nasty, poisonous, venomous, acrimonious, rancorous, splenetic, cruel.

▷antonyms benevolent.

malignant Oxford Dictionary of English