Question: If someone asks me if they should do something wrong and I say sure why not, and they do it and something seriously bad happens to them, would I have any karmic results? Wasn't it just their own karma to have that something bad happen to them? Probably they would have done what they did whether I said anything.
Response: Whether the person was "destined" to have something bad happen to them, you had the free will to encourage them or to try to dissuade them from what you knew to be wrong. By not trying to dissuade them, at some level you made the decision to encourage them in a wrongdoing. You chose to do what was either morally or legally wrong. Irrespective of what they decided to do and whether they got caught, you chose to do something wrong.
It's all shades of gray. If you said to not do it and they did, that's one karmic result for you. If you tried to talk them out of it and when it didn't work, you gave up and said "oh go ahead," that's another karmic result. If you thought what they wanted to do was fine even though you knew it was wrong, that's another karmic result. It's all shades of gray.
You may now be thinking that you were also "destined" to say what you did.
Your destiny resulted in who you are, in what you were taught, and the circumstances in which you are living. But your every thought is not predestined. Even if having that fated conversation with your friend was destined (and I do not know if it was or wasn't) every word in it was not. At any moment, we have the potential to turn away from doing something wrong, from harming another person or being, and making the morally right decision. By making that right decision, we will redirect to some degree our future.
But if we chose the wrong decision—or encourage someone else to make the wrong decision—we will undergo the karmic consequences for what we have said or done.