Brink

I did this on a Free Play session on Shipyard.

Game mode: Objective
Play mode: Solo
Match settings: Min Team Size = 0

Make sure you start at the resistance side and go to the command post. Become an engineer and build the barricade in the middle, just opposite the crane you need to defend. After you build this barricade select the objective wheel and chose to build the side barricade. The location will show up in your screen. Just build the 2 barricades and finish the round.

If you do this you will also unlock:

This achievement requires you to be on the defending team, and essentially 'Skunk' your enemy. Most missions have two phases - Once the primary objective on a level has been achieved, there is often a cutscene followed by another primary objective. The achievement requires you to deny your opponents that cutscene.

This is another one that I got as RESISTANCE forces, on the mission Day 1: Getting Answers. This level features only one primary objective* and one secondary objective, so it's likely that most of the bots will cluster around the doors.

From your menu, select Campaign, then the mission 'Day 1: Getting Answers'. Ensure your setting are set to Solo play, so nobody interferes, and set the difficulty to easy to ensure the quickest success.

Security Forces will be attempting to plant a charge and open one of two doors located on either side of a small boiler room. You will want to be an Engineer to ensure you can disarm any hopeful charges they manage to plant.

At the beginning of the match, race to the objective room and spend some time familiarising yourself with the room. There are several places where light and medium body types can SMART up into clever hiding places or vantage points to keep an eye on the door(s).

Of course, there's only one of you, so finding the quickest and easiest ways to transit between the two doors is reasonably important, but if you're having any trouble, simply invite in a friend, or come back when you've got a turret.

** I said there was only one objective. Whilst this is true, I failed to notice immedietely that the objective room contained two doors, and the Security Forces would get through one door, with me sitting in the other, utterly confused at my failiure. Just ensuring this doesn't happen to you (Although I doubt everyone's as unobservant as yours truly.)

This level is also an ideal place to grab the achievements "Oh I'm sorry, was that yours?" and "Use the wheel, earn more XP", although these are easily obtainable achievements.