小三不好惹
[xiăo sān bù hăo rĕ]
It roughly means 'The third party (mistress/concubine) is hard to deal with'. '小三' typically refers to a mistress or concubine in a marriage, which reflects the phenomenon of extramarital affairs in some Asian culture. However this kind of expression also carries a negative meaning reflecting social inequality and lack of morals. Note: We should promote healthy relationship models and avoid inappropriate labels to people.