beastly

adjectives

very unpleasant
"hellish weather"; "stop that god-awful racket"
is derived from
resembling a beast; showing lack of human sensibility
"beastly desires"; "a bestial nature"; "brute force"; "a dull and brutish man"; "bestial treatment of prisoners"
is derived from
is derived from

adverbs

in a beastly manner
"she behaved beastly toward her mother-in-law"