Brutal, a.
Etymology: [Cf. F. brutal. See Brute, a.]
1. Of or pertaining to a brute; as, brutal nature. "Above the rest of brutal kind." Milton.
2. Like a brute; savage; cruel; inhuman; brutish; unfeeling; merciless; gross; as, brutal manners. "Brutal intemperance." Macaulay.
Shades of meaning
Fernald has no entry of its own for brutal; he lists it under barbarous, brutish.
Where he writes about it:
A brutish man simply follows his animal instincts, without special inclination to do harm; the brutal have always a spirit of malice and cruelty. — from brutish