something that teaches one what not to do; a person or event used as a lesson on how to avoid mistakes or bad behavior

Someone who serves as a negative example from whom others can learn what not to do.

villain or negative character in a work of literature or art; also used generally for a person whose actions are condemned or criticized; opposite of a [[正面人物|正面人物|zheng4 mian4 ren2 wu4]]

to turn against someone and forget previous kindness or friendship; to suddenly become cold and heartless

The reverse or wrong side of something; the backside; the opposite side of a problem