Imagine person A of your OTP as a soldier in the wrong side of a war and person B is one of the prisoners. But then the soldiers receive a message from a higher ranking officer saying that they have to kill the prisoners and person A has to be the one kill person B. (Bonus: Person A has silent tears falling down their face when they execute B)  (Double Bonus: Person C has to drag person A away from Person B’s lifeless body)