Just like "Fall to Death", this is the second in a series of three achievements that you get from grabbing enemies and throwing them over the edge of a high place instead of trying to punch or use other powers on them. This is for tossing 50 enemies.
I've found the best places to rack these up are in Mephisto's realm. The Sepulchur (and some surrounding areas) is a good place because you can get pretty near to the edge and the enemies respawn infinitely.
Just stand near any ledge near an infinite drop off, grab enemies as they approach and then toss them over. The best way is to face away from the edge and toss them backwards over your head by pushing the stick in that direction. You can also do this with a side toss. However, if you try to face the ledge and throw them forward they will usually bounce off an invisible barrier, never falling to their death. Ultimately you need 500 in the demon toss marathon (at 1 point per demon) to get the third and final achievement in this series.