To get this achievement you have to completely upgrade your Exo suit in the campaign. In order to fully upgrade your Exo suit you'll need to complete Exo challenges to get upgrade points. The challenges and there Max out numbers are
Intel- All 45
If you complete all of them you'll have enough points to max out your Exo suit. All the challenges are pretty easy, they can NOT be farmed by reloading checkpoint though but here are the easiest ways I found to get them done.
Kills 1600- After the campaign you should have around 1400 kills, simply replay a few levels to get the remainder.
Headshots 175- this challenge is pretty easy, I got it midway through the campaign without even going for it, if you don't have it by the end of the campaign, simply reply a few levels aiming for enemies heads.
Grenade kills 320- I recommend using your smart grenades whenever you have some throughout the campaign. Also kills with the "MDL" gun count as grenade kills so pick one up whenever possible, if you don't get it by the end of the campaign, Load up the mission "crash" on recruit, After you land there should be a MDL sitting besides the box in front of you. I used this gun and smart grenades throughout the mission to earn heaps of grenade kills also refilling ammo whenever I could.
Intel All 45- the intel is fairly simply to find, use a guide on youtube if you're having trouble, most of the intel is pretty obvious though. I only had to look up a guide for 1 intel.
After all the challenges are done, upgrade your Exo suit between missions on the main menu. :)