Humans are funny creatures. It is very easy for us to get our feelings hurt... to become wounded by the acts of others. So what do we do when someone hurts us? We are sad, angry, pissed off... and of course we think of revenge. We see revenge as Karma for what others have done to us.
But revenge is not Karma. It is a reflection of our selfish need to strike out like a child who has been wounded. When we exact revenge on others all we do is damage ourselves even further. We bring shame upon ourselves and lower ourselves to the level of those who hurt us in the first place. Taking revenge doesn't make you a douche bag. Don't ever think that,remember this... we are only human. We all make mistakes, even the one's we get revenge on. Accept what you did, accept what the person did and let it go. You are the worst karma you will ever have. But we must strive to be better than that.
Always remember the universe doesn't punish it only knows cause an effect. We punish ourselves and each other more than enough to create Karma. That is why acceptance of our actions and then letting them go is so important in life.