Implacable /(?)/

Im·pla·ca·ble

Implacable

a.
  1. Not placable; not to be appeased; incapable of being pacified; inexorable; as, an implacable prince.
    I see thou art implacable.
    An object of implacable enmity.
  2. Incapable of being relieved or assuaged; inextinguishable. [R.]
    O! how I burn with implacable fire.
    Which wrought them pain Implacable, and many a dolorous groan.