When it comes to describing someone's behavior as unpleasant or savage, "in a beastly manner" is a common phrase that comes to mind. However, there are several other synonyms that can be used to convey the same meaning. For instance, you could say somebody acted viciously, savagely, cruelly, or ferociously. Alternatively, one could describe the behavior as uncivilized, barbaric, brash, or reckless. All of these synonyms share an underlying connotation of uncouthness and lack of refinement. Whether you're writing creatively or reporting factual events, using a variety of synonyms can help you to diversify your language and convey the intended meaning effectively.