With the addition of Halo Reach now within the MCC, this achievement has become a lot easier to obtain than the above solutions.
Go to the Campaign in the main menu and select Halo Reach. Go to Mission Select and then pick "The Package
". Choose to start from the Beta Waypoint
. You can also set this to EASY
to make it faster. Once complete, start the mission.
When you begin, sprint inside the ONI Sword Base, progress past the platforms leading up with all the Skirmisher on them until you trigger a piece of dialog stating something along the lines of "Where do we go now
". You should now see a big blast door that you must go in that will progress the mission and a CHECKPOINT
should trigger outside the door. Once the door opens, if you look up you will see a floating Engineer
at the back of the room. Scope in and kill it, once it is dead then press
on PC and then hit "Reload Last Checkpoint
", this will spawn you outside the blast door again, run in and kill the Engineer, rinse and repeat.
Here is a quick video of an easier way to obtain the achievement in Halo Reach