雷公打豆腐

léi gōng dǎ dòu fu

the God of Thunder strikes bean curd

fig. to bully the weakest person; to pick on an easy target

雷

léi

thunder

公

gōng

public

打

dǎ

a semantically light, transitive verb that is combined with various grammatical objects to form compound verbs and verb-object phrases with a diverse range of meanings (e.g. 打傘|打伞[da3 san3] "to hold an umbrella", 打電話|打电话[da3 dian4 hua4] "to make a phone call", 打針|打针[da3 zhen1] "to get an injection", 打手套[da3 shou3 tao4] "to knit gloves", 打氣|打气[da3 qi4] "to inflate")

豆

dòu

legume; pulse; bean; pea (CL:顆|颗[ke1],粒[li4])

腐

decay