良藥苦口

good medicine tastes bitter (idiom); fig. frank criticism is hard to swallow

mouth / classifier for things with mouths (people, domestic animals, cannons, wells etc) / classifier for bites or mouthfuls

bitter / hardship / pain / to suffer / to bring suffering to / painstakingly

good / very / very much

medicine / drug / substance used for a specific purpose (e.g. poisoning, explosion, fermenting) / CL:種|种[zhong3],服[fu4],味[wei4] / to poison

good medicine / panacea / fig. a good solution / a good remedy (e.g. to a social problem)

lit. bitter taste (cf good medicine tastes bitter 良藥苦口|良药苦口) / fig. earnestly (of warning, advice)