one bad apple can spoil the barrel

English

From the observation that rot of a single fruit can spread to many fruit nearby.

One bad person or element can have a harmful influence on many others.
Synonym: one bad apple can spoil the whole bunch

"One of our kittens started chewing on the chair the other day and now they're all doing it! Just goes to show that one bad apple can spoil the barrel."

one bad person or element can have a harmful influence on many others

Hindi: एक गंदी मछली पूरे तालाब को गंदा कर देती है (hi) (ek gandī machlī pūre tālāb ko gandā kar detī hai) (one dirty fish dirties the whole pond)
Latin: pomum compunctum cito corrumpit sibi iunctum (la) (a bruised fruit quickly corrupts the fruit next to it)
Malay: sebab nila setitik, rosak susu sebelanga (ms) (because of a drop of indigo, the whole container of milk is spoiled)
Urdu: ایک گندی مچھلی پورے تالاب کو گندہ کر دیتی ہے (ur) (one dirty fish dirties the whole pond)