Let's say one day you wake up in a dark room. In front of you, there is a person who looks exactly like you. A voice over the loudspeaker tells you that the person standing in front of you [i]is[/i] you, from a parallel world. They are an identical copy; they have lived the exact same life as you, down to the tiniest detail.
The voice tells you that he will give you, say, a 100 million dollars, if you kill that alternate universe version of yourself. This will hold ramifications for the alternate universe -- if you have a wife, the AU wife will be sad, obviously. The same can be said for your other loved ones: your friends, your parents, etc. Your AU self will be completely gone from their lives, likely with the cover story of a fatal accident.
If you decide not to do it, your AU self will return back to his normal universe and life.
So, would you do it? Would you be willing to cause distress to your loved ones; even if you will never actually have to see these "loved ones" ever, since they are only AU versions?
After you finish answering that question, ask yourself this: would your answer be the same if that AU version of yourself was instead replaced with a complete stranger, from the same AU? As in, would you kill a complete stranger -- a stranger belonging to a parallel world -- for the sake of money?
Finally, the last question: would your answer be any different if the person you had to kill was a complete stranger, from[i] our[/i] world? (You do not need to worry about being caught)
*AU = Alternate Universe
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I did it in Borderlands. Why not do it in real life?