Eagle Strike and Stunts on Carlo Grimaldi
http://www.youtube.com/watch?v=p9WERaAl6Mg
Here is a description of the video.
Eagle Strike: This could be considered killing him where he stands. Carlo's travel pattern depends on where you are and if there are any live guards nearby. If you kill every guard before you start the scene Carlo will stop at the bottom of the stairs. Jump from the roof and grasp the bottom of the stair railing.
Eagle Dive and Strike: After you kill every nearby guard move Carlo in place for an eagle strike or eagle dive (ledge assassination instead of air assassinaton). He can't be grabbed at full health so either punch him several times or attempt to grab until he moves in the right spot. Apologies that I couldn't assassinate him right when I grasped the ledge (the camera wasn't facing him directly). 
Additional Stunts: Right after the scene quickly run out of the room and jump to the bottom of the stairs to kill Carlo before he can run farther. I also did a far range air assassination.