一颗老鼠屎坏了一锅汤

yī kē lǎo shǔ shǐ huài le yī guō tāng

lit. one pellet of rat feces spoiled the whole pot of soup (idiom)

fig. one bad apple can spoil the whole bunch

one

classifier for small spheres, pearls, corn grains, teeth, hearts, satellites etc

lǎo

prefix used before the surname of a person or a numeral indicating the order of birth of the children in a family or to indicate affection or familiarity

shǔ

(bound form) rat; mouse

shǐ

feces; excrement; a stool

huài

bad

le

(completed action marker)

one

guō

pot; pan; wok; cauldron

tāng

soup