Halo Wars

This one is simplistic as well as a piece of cake. You need to simply send your partner 5,000 or more supplies in a match and win.

Ok, so for this one, you'll want to start up a Skirmish 2v2 on Memorial Basin. Make sure you pick Sergeant Forge (because he builds Heavy Supply Pads right away) for yourself and the other three AI are insignificant. Set the difficulty to easy and always have the mode set to Standard. So when you start, build a base full of supply pads, send your Warthog out and collect as many supplies as your little car can muster. Then build two precautionary turrets just in case they attack. Behind your base, either to the left or the right is a vacant base, when you have enough money go back and purchase it. Build two Reactors and a Vehicle Depot. Then upgrade the base and build two more Supply Pads. One more base upgrade and build two more Vehicle Depots - that way you'll be able to train your Scorpions much faster and more efficiently (one in each Vehicle Depot at a time). Then while you're building that and have enough money to spend, upgrade one of your Reactors and make it Advanced so you'll have a Tech Level of 3. You'll want to build 10 Scorpions, putting you at the set population limit of 30. Now that you have a higher tech level, research the "Canister Shell Ability" and as soon as that bad boy is researched, rush the enemy bases and be sure to use the "Canister Shell Ability" by pressing "Y" on the target you want to hit. You have to do this and attack for yourself because the Computer AI, especially on Easy, is, well, how do you say... "Challenged". Ok almost done, BUT WAIT!! While you're units are attacking and before you destroy the final base, be sure to send your partner 25 clicks of 200 Crates, totaling 5,000 Crates. To send your partner money, go to one of your Supply Pads, and to the right click on "Send Supplies". Do this 25 or more times and finish off the enemy and after it says your last enemy is defeated, the Achievement will pop up so freshly, you'll think of comparisons like how awesome it is when popcorn pops up in such a fresh manner when you microwave those little kernels in your kitchen.

GOOD LUCK!!

Get this and Drain Cleaner in one go.

Start a standard 2v2 game on Memorial Basin, easy difficulty, with you as the Arbiter, your teammate as anything, and your opponents as random Covenant.

Start by building a warehouse and queue up a temple and another warehouse, and send your Ghost around to pick up resources. As your warehouses are built, upgrade them to Blessed Warehouses. Take two more bases (one next to you, one next to your ally who will be unlikely to take it himself), and fill them with Blessed Warehouses. You may also clear out a nearby reactor and staff it with a unit of Suicide Grunts (which you can build from the base core without building a Hall), which will save a little time. Along the way, spend extra resources upgrading your leader abilities to maximum. Fend off attacking armies from you and your ally as necessary.

Once your abilities are maxed, wait until you have just over 5000 resources. Select a warehouse and donate all of it to your teammate. Now, select the Arbiter and go into Rage mode. Walk around the map taking out enemy units and reactor guards until the Drain Cleaner achievement pops. Do not exit Rage until this happens -- you lose no resources by walking, and what you do lose by attacking will refill quickly. Because your enemies are Covenant and not UNSC, they will be unable to stop your Rage with a Disruption Bomb. If, after all reactors and enemy units, you still come up short of 20, just walk the Arbiter away (with your left stick; stay in Rage) and hang out until more enemies are built.

Once Drain Cleaner pops, take your Arbiter to the enemy bases and go to town. Two Memorial Basin achievements, one game.

you can actually get a two for one in this match
make a 2v2 on memorial basin and make your enemys be arby 'n' the chieftan, and your teammate anders, and you be cutter. now just build a reactor and 4 supply pads and wait, once theyre all ready, upgrade them all, starting with the supply pads. once that is done, upgrade your base and make a barracks and another reactor. now upgrade the marines twice and send some out to take over the supply elevators so that you can get a lot of supplies really fast. and once you have odst's, send out a lot of them to take cover in the crashed warthogs and pelicans, after that the enemy should be trying to get some units out, but with your odst's they shouldnt be a problem, but you should just take the bases around yours as soon as you can. and be sure to make them supply bases, and now wait for 5000 credits, and send ALL of them to your teammate. but once that is done keep sending them just in case. now its time to kill off your teammate (harsh, but fair) just take out your odst's and put them in a corner with a few coloring books and theyll be fine, but try to lure the enemy to your temmates base, and hopefully there would be only one if you took all of the others. but once thats done get the newly destroyed base and destroy ONE of the enemies and take that base, and now you can bring back your odst's and put them back into cover around the map. now just keep destroying the enemy until you have 4000 without killing him off. it should be pretty easy if your odst's all have 3 stars of veterancy with some skulls turned on to speed things up, but not boomstick because that one sucks. but right before you kill him, turn on all of the skulls that give you an extra point multiplier. and just kill him after all of that anticipation, kill him, and once you do, you should get the acheivables "titan" and "never leave a man behind".