Chapter 14 - Return to London Nautica
"Can I play, daddy" difficulty
5 kills within 10 seconds using dual-wielded rocket launchers.
This is after you fight through the first room you get to after you swing on the rope. Then you cut two chains on a scaffolding (piece of wood held with 2 chains), then you walk down and you cut one more chain holding this scaffolding in front of you, making it drop down on one end like a ramp. Run and jump the gap to land on a balcony. As soon as you open the door, you will see a soldier run away. Dual wield your Assault Rifles, and press left and right on the D-pad to get rocket mode on both of them (you only need rockets in one chamber, doesn't have to be ammo in both, but don't try to fire with the second gun if it is empty of rockets, as it will auto switch to machine gun). Once you have the dual assaults equipped, set to rocket mode, and reloaded, move on through the hall and the soldier that had run away will be shooting at you. Start running, go past him, and about 1 foot away from him, on the same side of the hall that he is on, there will be a door. Go in there, and stand behind a wall / look at the desk like I am doing in the video. That will make him and his friends advance to your position, and because it is a tight room, they will all be jumbled together, allowing you to get multi-kills. Then just kill them. You should be able to easily get all 5 in 10 seconds (as long as you do not blow yourself up with a rocket).
I did this just accidentally in the video (wasn't trying to make a guide, just playing through my game, hence the 30 second "Xbox Record That" lol), but I since then replicated it a few times to see how well it works, and I was able to do it every time very easily (except for 2 times out of the 20 I retried, as 1 time I got shot to death for not running to the room fast enough, and the 2nd time I blew myself up with my own rocket because I was in the soldier's face).
The part starts at 1:12 of the video, the guy I am talking about is at 1:18. Right past him down the hallway is the door, behind the cardboard boxes.
My video below should help explain the actual shooting and it shows that you do not need rocket ammo in both guns, just need them both to be in rocket mode.