S: (adj) beastly, bestial, brute, brutish, brutal (resembling a beast; showing lack of human sensibility) "beastly desires"; "a bestial nature"; "brute force"; "a dull and brutish man"; "bestial treatment of prisoners"
Adverb
S: (adv) beastly (in a beastly manner) "she behaved beastly toward her mother-in-law"