Zabora Lionheart
X-Yami-no-Ko-X
I wouldn't use the word karma but there still would be consequences. Take the "come back to me" example. There's probably a reason that person left and no matter who performs it it's forcing whoever it is to come back and it will probably make both parties unhappy.
I think what people tend to forget is that there's consequences for everything we do. Good and bad.
But do you believe that would come back on you or the caster or both?
In general, I would say the person who wants it done in the first place. Because they are going to be the ones living with the results. In the example of the "come back to me" Person A wants Person B so they go to Person C. Generally, I would think, that person C would never see Person B or even if they did know they would ever tell them so it would just be Person A who has to live with a very unhappy Person B or Person B could try to make Person A's life a living hell because they can't get away.
People tend to really view magical consequences as "Oh the universe is going to send something your way depending on what you do" but really I see the consequences come on a more mundane level. If there really were this Three Fold Law as the way most witches define it then the corrupt wouldn't win and the good people wouldn't suffer. I'm trying to think of some real life stuff that either me or one of my friends have done but I can't really think of anything.