A bad peri can be described by a variety of synonyms that capture various aspects of its negative impact. One synonym could be "horrible," emphasizing the extreme discomfort or pain it can cause. Another option could be to use "unpleasant" or "uncomfortable," focusing on the discomfort without necessarily suggesting intense pain. "Aggravating" or "annoying" could also be used to describe a bad peri that disrupts daily activities or causes ongoing frustration. Overall, the choice of synonym may depend on the specific characteristics of the bad peri and the tone or context in which it is being discussed.