Supreme Commander 2

The best way to do this, is to go against an easy AI on a large map (try Satan's Clutch) with lots of mass deposits, and on Supremacy mode. Wait for the AI to build a mass deposit away from their ACU, then get a load of gunships and kill the ACU.

LEAVE the additional mass extractor alone, or your game will end. After you've destroyed the ACU, build your own mass extractors and research any available mass bonuses aquired by research. (I recommend Aeon / Illuminate for this, they seem to have better bonuses)

After that, sit back, go watch a film, and the majority of your mass should be completed. This can also be used in tandem with the 24 hour achievement. (Please see the guides for their achievements for more details.)

I got +111 mass per SECOND, which is 6600 a minute. 1,000,000 divided by 6600 is 151.5 minutes, which is how many minutes you've gotta wait. Remember, that the number is cumulative, so you'll need a little less.

This achievement only pops after you've become victorious, so if it doesn't pop when you win, you've not harvested enough mass.

This solution is to add to others, as those already provided are pretty good.

Field of Isis is a pretty good map for this achievement. If you play as UEF with the Mass Income upgrade on Supremacy mode and capture 39 of the available 40 mass deposits, your mass income will be 63 per second. That's 3,780 per minute or 226,800 per hour. This means after about 4 and a half hours of having all mass deposit, you'll have made it to 1,000,000 mass. And that will also contribute towards the Time Cruncher achievement (which requires 24 hours of play in Skirmishes or Online games):



Maelstrom26's guide will take about 2 and a half hours to unlock this achievement, as opposed to 4 and a half, but as you've got to play for 24 hours to unlock Time Cruncher anyway, you may as well take your time.

As Tazwas said in their solution, position your character at point A and the AI at point C. I recommend taking the mass extractor which lies halfway between those points and heavily guarding it with four anti-air and four anti-ground turrets. This will prevent the opponent advancing towards your position and moving out towards the mass deposits on the other side of the map. As soon as you can, I'd also research the shield generator and build some next to mass extractors which are likely to come under fire. The ones furthest away from the opponent shouldn't need any protection but the closer ones will, especially if you intend on working towards the achievements for units (see below).

Once you've built all the mass deposits you can, I recommend building energy generators until you've got a decent energy income (about 200 per second). Then, build a mass converter and keep converting energy into mass. To do this, select the mass converter with , hold and then keep pressing to spend 1,000 energy and convert it to mass. I am not sure exactly how much mass you get for every 1,000 energy but it seems to be about 150-200.

While working towards this achievement, you can also work towards the Sharp Shooter and Master Builder achievements:




Station an army close to the opponent (but not close enough to destroy their factories or mass extractors). Allow them to continue sending wave after wave towards you. Have at least one of your factories set to repeat build (after selecting the units to build, hit ) and set the factory's rally point to the position of your army. You can do this by selecting the factory with , moving the crosshair to your army's position and hitting . It's going to take quite a few games for these achievements to unlock (especially considering the 200 unit cap in skirmishes) but it all adds up! Note that if the AI is set to easy, you're unlikely to see as much action as on normal, hard or cheating. I'd go with hard for a decent number of units. Also, make sure to fully upgrade the unit types you are using. I'd recommend having an all land army, but an all air or a mix of land and air will do just as well. Rock heads have quite low health and so are perfect for getting constantly destroyed and rebuilt.

Here's an overview of one of my maps in a Fields of Isis skirmish:


I did try to take a video of my map after unlocking the achievement, but after the latest update the Xbox decided to change my default setting for recording from 5 minutes back to 30 seconds, so I'll redo it using the same method I've explained above and upload another video of the last five minutes at a later date.

THE SETUP:

From the main menu select: SKIRMISH

Map: Fields of Isis

Game Type: ASSASSINATION

Rush Timer: OFF

PLAYER 1 (which is you)
Team: 1
Faction: UEF
Color: Pick your favorite color
Starting Position: A (use to select starting position if necessary)

PLAYER 2 (computer player)
Team: 2
Faction: UEF
Color: Pick the color you hate most
AI Profile: Hard
Starting Position: C (use to select starting position if necessary)

THE METHOD:

The method is explained in the video below.

The achievements will ONLY unlock after you have COMPLETED the match

ACHIEVEMENTS