I believe Karma occurs when you throw out negative energy. When you purposely do something that you KNOW will hurt another person, yet do it anyway for your own selfish reasons. This could happen in any aspect of life, when you go out of your way to cause dilemma to another persons life but you asked about affairs..... What is the karma for having a affair? It could be many things, For the other woman, maybe she'll spend weeks, months, years waiting in the background for the married man to leave & he never does, the other woman is left feeling heart broken & used KARMA. Maybe the married man leaves his wife for the other woman & in turn cheats on her throughout their relationship KARMA. Maybe the married man leaves his family for the other woman, looses everything he has & the other woman then decides she doesn't want him anymore KARMA. Nothing good can ever come from intentionally hurting another & that IMO is karma. You get back what you put out