Characterized by intense ill will or spite
So intense as to cause extreme suffering
Showing or suggesting a disposition to be violently destructive without scruple or restraint
Prone to cruelty
She thinks she is some kind of vicious animal.
This was not a mangy or vicious creature standing before him, but a breathtakingly beautiful, gigantic wolf.
A vicious circle is obviously involved.
I shall die! she muttered, wrenching herself from Marya Dmitrievna's hands with a vicious effort and sinking down again into her former position.
Subsequently this vicious principle was extended still further.