Kill 3 enemies with a single explosion
The Order: 1886 COLLATERAL DAMAGE
Load up Chapter 3 / Scene; The Puppet Queen and play a little further. You will come to this area where you will have to fight a lot of enemies. A grenade will be here you pick up every time. If you fail to get 3 enemies you can back out into the title screen and continue.
You will start exactly before the grenade and have a chance to try this over and over.
Go into the top building with the blown out windows and look right. A few enemies will shoot you from this position and will for the most part stand in the same position. Cook your grenade and throw it at the to get this trophy.