When it comes to finding synonyms for the phrase "pain in the rear," there are a plethora of options available. Some alternatives include "annoyance," "irritation," "nuisance," "hindrance," "bother," "trouble," and "thorn in one's side." Other options may depend on the specific context or situation in which the phrase is being used, such as "difficult person," "challenging obstacle," or "tedious task." Regardless of the specific phrasing used, these synonyms all communicate the idea of something being unpleasant or bothersome, making them effective alternatives to the potentially crass or unprofessional connotations of the original phrase.