Thomas Aquinas

“ On the other hand, cruelty not only regards the default of the person punished, but exceeds in the mode of punishing: wherefore cruelty differs from savagery or brutality, as human wickedness differs from bestiality, as stated in Ethic. ”

“ Clemency is a human virtue; wherefore directly opposed to it is cruelty which is a form of human wickedness. But savagery or brutality is comprised under bestiality, wherefore it is directly opposed not to clemency, but to a more excellent virtue, which the Philosopher (Ethic. vii, 5) calls "heroic" or "god-like," which according to us, would seem to pertain to the gifts of the Holy Ghost. Consequently we may say that savagery is directly opposed to the gift of piety.
Reply to Objection 2: A severe man is not said to be simply savage, because this implies a vice ”

“ Consequently it is evident that it is comprised under bestiality: for such like pleasure is not human but bestial, and resulting as it does either from evil custom, or from a corrupt nature, as do other bestial emotions. ”