Section 8

The only problem you are likely to have is the campaign mission you must complete before getting this achievement called Operation Liberation where, after mopping up enemy forces and taking down a blockade, you are forced to escort the universe's slowest convoy vehicles. Don't be impressed by the tanks at both ends of the convoy, their usefulness is precisely zero because the AI inside them can't aim and you're not allowed to get inside.

First and foremost, detpack the first two guys that spawn right after the commander on the comm says "You have your orders, convoy leader". You'll definitely kill one and will at least drop the shields on the second. Afterward, run back toward the convoy and resupply with detpacks at the supply depot, then continue past the convoy.

Ignore the infanty that burns in (signaled by one of your teammates yelling "Arm burning in above us!" or something to that effect) but destroy the rocket turret they bring with them immediately. Run past the convoy again and creep up to the large building just ahead.

Inside are two of those annoying mech suits with the mounted machine guns. You are going to die tons of times here but it is imperative you destroy or heavily damage both heavy armor suits until the convoy reaches the entrance.

When the convoy gets that far, you need to ignore all enemies nearby again and dash ahead. There are two turrets on either side of the road just outside the building that will tear up your convoy vehicles and you must destroy them with haste.

At this point, all that's going to save your remaining convoy vehicle (guaranteed there will only be one) is abusing the golden rule of video game AI -- the player is the priority target. Draw as much attention to yourself as possible by taking potshots at all enemies in your line of sight, and when they're all focused on you, hide somewhere that requires them to completely reposition to get a shot. The enemy AI on Section 8 focus their efforts like laserbeams and will completely ignore the convoy (even moving around the vehicle) to shoot at you, so how long you can manage to stay alive at this point is how long the convoy will continue to survive.

This is the only difficult mission in the entire campaign, so breathe a sigh of relief when you finally get this achievement because you'll never have to play it again.