First of all, as others have already pointed out, this certainly didn't take place in Singapore.
And from their comments (on Stomp, Singapore Uncensored, Facebook etc), Singaporeans don't seem to realize that this particular incident is mild, by China standards.
In China, it is common (like, several such incidents every day? you know how big China and its population is?) to have the wife and her own gang of 6-8 friends (usually women, but sometimes include men) not only totally strip naked the mistress in public, but also thereafter viciously beat her up without mercy for prolonged periods (with dozens or hundreds of members of public around watching, no one dares to intervene) until the crying/screaming/begging mistress is all bloody and losing consciousness, sometimes shaving the mistress' head bald, with 2-3 of the wife's gang filming the incident on their handphones to upload her humiliation online permanently on the internet (ostensibly so she won't dare to look for the husband again).
Common ethical decency sense dictates that in such a scenario, the worst karmic perpetrators are : the wife, followed by her participating gang members, followed by her husband (especially if he was present but didn't even try to stop the wife), the members of the public who just watch without intervening in the public mob lynching, and lastly, moreso the victim than a perpetrator, the mistress herself (who may have been lied to and not even know the cheating husband is married, and/or it was the husband who, sick of his ugly fat wife, actively pursued after the mistress).