QUOTE(milesk182 @ Nov 2 2010, 05:17 PM)
Um i tried this for about a week and finally figured out something. If you land on curved ground it will not kill you so it wont count. I have watched this video and copied it many times. I found that the dirt was the flattest compared to the grass. Try hitting the elite without assassinating him and you will see that you wont die on certain falls. When you do, u will know where to assassinate him. Hope that helps, It needs to be a flat ground not slanted at all. If your body SLIDES even a bit BEFORE YOU DIE it will not count! Goodluck.
im not sure it has to go with the ground so much as where you land relative to the elite, if you land ON the elite its not a fatal fall, so even if you get the cinematic assassination you dont get the achievement
also, as bong says you need to turn off sprint on the way down, because if you land while sprinting its not a fatal fall
i found it helpful to try to time it with the voiceover in the game, been a few weeks but IIRC i seemed to get the closest when jumping off just as emile says "race you to her"
too me about 3 solid hours of trying in order to get it, i have no idea how many times i jumped during that time lol