Perform 5 consecutive kills without being spotted by an enemy (2)

You can get this in the first chapter when you reach the Korean base of operations. There will be reinforcements called in and you can maintain stealth and individually take out each one without being spotted from a distance. If you are spotted you can restart checkpoint. There are also various other locations you can get this trophy later in the game as well, if you see a large group of enemies throw a nade from cover and if it kills all of them you will also get this trophy.