When it comes to describing someone who is easily irritable or prone to outbursts of anger, there are plenty of synonyms for the term "bad-temperedly" that can be used. Some other options might include "irritably," "testily," "crankily," "crossly," "surlily," "fiercely," "grouchy," "petulantly," "grumpily," "brusquely," "snappishly," "short-tempered," "cantankerously," "irascibly," or "peevishly." Ultimately, the specific word choice will depend on the context and tone of the writing, as well as the degree of intensity or aggression being conveyed. Whatever word is chosen, it should aim to convey a sense of someone who is easily provoked or annoyed, and who may not be pleasant to be around.