Halo Wars

Best attempted on easy, at the begining of the mission move all your units towards the back of your base and refrain from building any units as your turrets should be able to deal with anything counter attacking once upgraded, now the tedious process of repeatedly mac blasting the scarab begins if you have the emperor skull collected from the final mission activated this reduces the mac regeneration time in half, otherwise it will take about 20mins to destroy.

As the Scarab becomes damaged it may start randomly destroying cover blocks including the ones protecting your base, however don't panic as in my experiences if you sit tight it tends to destroy the front block and move on

OK this is a quicker method of getting this achievement for all those impatient people out there like me. Start up the mission on Easy and send all your troops to the back of your base.

Use all your remaining base squares for resources and upgrade each one when you can. Upgrade all your turrets and start getting all the upgrades for the warthogs. During this time use the Mac-blast on the scarb as much as you can.

Once you have all the upgrades for the warthogs start producing warthogs as fast as you can (The Pain Train Skull will help). Once you have at least 10 warthogs send them all to attack the Scarab but leave any other unit types behind. Now continually produce warthogs and send them in to attack the scarab. For speed you must also use the Mac-Cannon whenever it is available (The Emperor skull will allow you to use this more often).

It is possible to avoid the scarabs beam by moving to the opposite side the beam is about to move to but you will still lose some units (The Sugar Cookies skull may help a bit but is not necessary). Once the scarab gets down to about half health it should ignore your warthogs and concentrate its fire on the blocks outside the front of the base.

Using this method you are will be able to do this in under 10 minutes. (It took me 9minutes 30 and I didn't have the Emperor skull or the Sugar Cookies skull)

Completed this Achievement in 5:46 by doing the following combination of the above tactics with one small twist.

Used Emperor, Pain Train, and Bountiful Harvest Skulls and set the difficulty on Easy.

Make all supply pads, crank out warthogs like crazy, and upgrade to gauze cannons. Constantly use the MAC round charge everytime it is up. The small change was do not send in the Warthogs until after the scarab is at 50%. At that time he will almost never target your hogs, instead targeting the area near your base (and the walls in front of it).

I got this achievement by a variation of the latter method; instead of sending volleys and waves of warthogs to the Scarab, I sent teams of three to four Warthogs, getting the appropriate upgrades and queuing them to spawn. I used -no- skulls to get this achievement.

Also, at my base I just spawned Supply Pads and Reactors, along with the Vehicle Depot (just in case you need to make a wall of tanks). Amassing a lot of supplies isn't a necessity (just enough for at least 5 Warthogs at a time), but it will help if things go too wrong too fast.

Cobras and other vehicles would most likely work for this, too, but I chose mostly all Warthogs since they are faster.

Once you have a good number of them, have about three of them go to the upper left-hand corner of the Scarab, near the blue Supply Cache. When I played, the Scarab barely noticed these Warthog teams, and I used the rest of the warthogs to draw fire from the right side, trying to distract the Scarab. Combined with the Warthog fire and the MAC Gun, you can kill the Scarab quite quickly, and if the game does manage to last a while, use Warthogs as damage sponges to absorb the Scarab's beam so that the wall isn't destroyed.

If the wall IS destroyed, make a phalanx of vehicles like Scorpions and warthogs, also try to divert the fire with distraction vehicles. Essentially if the wall is destroyed you're recommended to restart and try again, but it's not impossible; by the time the Scarab destroys the entire wall it should be at least a quarter-ways dead.

Can be completed in about 5:00mins. Used Emperor, Pain Train, and Bountiful Harvest Skulls and set the difficulty on easy.

then make all heavy supply pads, build warthogs like mad and upgrade to gauze cannons. Constantly use the MAC round charge everytime it is available. Do not send in the warthogs until after the scarab is at 50%. By this time he will almost never target your warthogs, instead hewill be targeting the area near and around your base and the walls in front of it.

What you should do is play on easy and keep mac blasting it until it eventually starts attacking to walls to your base when it does that send all your units out the left side of your base cuz on the left side the power node is farther out and your units will be busy shooting the guys on the way there. It should still be attacking your base but if not when it looks near you only hide the scorpions. Remember to keep mac blasting and attacking it and you'll eventually kill him.

Easy difficulty, max out Warthog upgrades and make about 10+. Send about 3-5 at a time, switch them to the other side of the scarab as it turns its head and the beam approaches them. Fire pop shots with the MAC cannon. Once the Scarab begins firing at the ruins protecting the base send the rest of them in. Takes about 10 minutes