A great place to do this is in Thornfelt Swamp. When you first enter the area, you will have to break open several logs by having enemies aim at you, miss and hit the logs and so forth until you can make it all the way through. You can trick these enemies into aiming at and killing each other
Attached is a video I recorded showing how to do it, I use the two enemies at the end of that area. After one is dead, just move away from that area a bit and go back to respawn the enemy.
Any negative votes, please let me know why and any way that I can improve the solution.