sometimes I’m doing some trick then I land it does the assassination for a split second and does not activate I punched again and the same thing happened the guy turned around and killed me with a scattershot why?
Something that just happens sometimes, perhaps you were experiencing some lag or didn’t hold the button down long enough, orrrrr you were killed mid assassination and he just happened to turn around and shoot you with the scattershot. I know I have done it to people before, from both sides. Just happens mate.
Try holding the melee button for the entire animation.