Malignity, n.
Etymology: [F. malignité, L. malignitas.]
1. The state or quality of being malignant; disposition to do evil; virulent enmity; malignancy; malice; spite.
2. Virulence; deadly quality. His physicians discerned an invincible malignity in his disease. Hayward.
3. Extreme evilness of nature or influence; perniciousness; heinousness; as, the malignity of fraud. [R.]
Syn. -- See Malice.
Shades of meaning
Fernald has no entry of its own for malignity; he lists it under acrimony, enmity, hatred.
Where he writes about it:
Malignity is the extreme of settled ill intent; virulence is an envenomed hostility. — from acrimony
Virulence is outspoken; malignity may be covered with smooth and courteous phrase. — from acrimony
We say intense virulence, deep malignity. — from acrimony
Malice is a disposition or intent to injure others, for the gratification of some evil passion; malignity is intense and violent enmity, hatred, or malice. — from enmity
Malice is direct, pressing toward a result; malignity is deep, lingering, and venomous, tho often impotent to act; rancor (akin to rancid) is cherished malignity that has soured and festered and is virulent and implacable. — from hatred