Spin Doctor Trophy
Kill two enemies with one throw of the Battle Disc
The Battle Disc is a weapon that the Predator uses. When you pick it up, look in your inventory for a disc with sharp edges. To use the disc just aim with and use the analogue stick to choose the direction, now just let go of to throw it. This can be very tricky because you need to have 2 enemies right near each other to get both kills. Simply kill 2 enemies with the one throw to get the trophy.
This can also be gotten on single player after you have achieved the battle disc. I recommend the last level on the bridge. A few aliens will attack you here so just try and get two aliens lined up and throw the disc. Just kill 2 aliens with one throw and the trophy is yours.
TIP: The Battle Disc is like a boomerang, therefore it will come back to you which gives you the chance of throwing it again. Also, you have the opportunity of hitting another enemy as it is on its way back to you. So try to aim it at the enemies again for a higher chance of success.
Just in case your are struggling, someone has posted a video of how to get this in single player. This is one a mission during the predators campaign mode: