The Riftbreaker

So first of all, any level wall counts. Building a few big bases will get you halfway there (maybe). If you don’t plan on playing the campaign again or many survival maps and just want to get this done there’s two tricks.

First of all, if you don’t know how to hold A and continuous build walls, you’ll want to do that (hold down RT if you want max level built). Redo all your base walls to triple thick (that gives room for two gates in front of each other), it shouldn’t affect your guns too much. I had to do do all my outposts too, as I visited for other reasons.

Also pick a few big areas and make a big square of walls, try and do this outside your base but in a path where hordes don’t usually come from (or near range of your guns so enemies will aggro your guns instead of attacking the walls forever). Just build the square inside out all walls. 25x25 is worth 525 wall segments or so.

I’m not aware of if one needs to have all wall segments at once or if it’s okay to mass sell them (use the tools menu so you can hold A and just cursor over segments to sell) and rebuild.

To get the Carbonium for this should be an issue as you probably have a few Carbonium Synthesizers going by now, but level 1 segments are 5 apiece.

I personally found this to be one of the more annoying achievements in the game. I hope this helps.