一马勺坏一锅

1. • one ladle (of sth bad) spoils the (whole) pot (idiom)
2. • one bad apple spoils the barrel

Character by character

• 一(yī)one
• 马(mǎ)surname Ma
• 勺(sháo)spoon
• 坏(huài)bad
• 一(yī)one
• 锅(guō)pot