Rancor /(răṉ"kẽr)/

Ran·cor

Rancor

n.
  1. The deepest malignity or spite; deep-seated enmity or malice; inveterate hatred.
    It would not be easy to conceive the passion, rancor, and malice of their tongues and hearts.
    Rancor will out; proud prelate, in thy face I see thy fury.
    Rancor is that degree of malice which preys upon the possessor.
    — Cogan.