ㄌㄧˋchīlìㄅㄨˋㄊㄠˇㄏㄠˇtǎohǎo

吃力不讨好
  1. 付出許多心力不但回報遭受嫌棄 警察取締攤販吃力不討好工作」。

arduous and thankless task (idiom)​; strenuous and unrewarding