You performed a drop assassination of at least 150 meters in the Kill Cascade challenge
The only kill that can be made from this height is the final target. From the first red target, look right to see a hillside with grass and rocks. Double-jump/Blink over to it and climb up the rocks on the left hand side. From here, Blink forward to the top point on the ruined building. Next, either jump ahead to the ledge on the opposite wall, or look to the right to see the red column indicating the final target. Jump and Blink straight ahead, and then angle the camera downward to see where you are going. Depending on how accurate you are with Blinking, you may need to do so a second time in midair to align yourself over the shaft and avoid hitting anything on the way down.
The last kill in the video below will earn you the trophy.