The state or quality of being malignant; extreme malevolence; bitter enmity; malice; disposition toward evil; intense ill will; as, malignancy of heart. [1913 Webster]
Unfavorableness; evil nature. [1913 Webster]
"The malignancy of my fate might perhaps distemner yours."
[1913 Webster]
Virulence; tendency to a fatal issue; as, the malignancy of an ulcer or of a fever. [1913 Webster]
A cancerous tumor that is spreading beyond the point of origin. [WordNet 1.5]