*THIS SOLUTION CAN WORK FOR ANY OF THE WAVES 1-50 ACHIEVEMENTS*
So I have completed this achievement on Heavy, Scout, Sniper and Engineer. Most people think insane is too hard and won't even attempt the achievement; constantly saying, "I'll never get this achievement," or even selling insane bounties. This achievement can be very easy if you have the right people.
You will need the following:
*** Spoiler - click to reveal ***A Scout with the following skill:
40%-50% fabricator increasement
An Engineer with the following skills:
* means the skill is optional
Level 3+ Fortification Health
Level 3+ Efficiency *
Level 3+ Barrier Health
Level 3+ Turret Health
Level 3+ Fortification discount *
The other classes are optional. 2 Scouts WOULD be better however that is completely optional.
On my first run through I was on Checkout. It is a VERY good map for an insane run. With this solution I would suggest to equip an insane bounty as you'll most likely get very far.
Here is a video for the set up:
Depending on the number of scouts, you should have at least 5100 energy. And depending on the Engineer's skills, you may be able to buy a turret. If you can, build one.
All players must be hanging back and shooting from the same area. You CANNOT risk going down in the middle of the battlefield. Once there is one enemy left, the scout will take a companion and collect the energy. It will collect about 1500+ energy in the early rounds.
Once you have enough energy, start to build turrets. DO NOT build a turret if you do not have over 6500 energy. If you do, do not use it as you won't be able to repair it.
Continue to pass waves and let the scout collect energy when there is one enemy left.
Around Wave 5 it will get more difficult. You should have 2 turrets around that time. You will also need to buy barriers and be putting them at the left wall, in between the shelf and wall. Then put a barrier on the right, in between the wall and the counter.
Continue to build turrets until you have 4. Only build 4. The 5th player should be the scout, who will go to collect energy and be the designated medic.
Around Wave 10 you should have about 3 turrets.
Waves will get increasingly more difficult.
You should only have 4 turrets at a time.
When it comes to upgrading the turrets, only upgrade if you will have 1000+ energy remaining. You still need to be repairing and refilling the turrets. It should be easy if you have a good scout.
Decoys can also be useful, but are not required.
Continue to do this for the remaining rounds. Comment any questions :)
~LiviPenguins