To obtain this achievement you need to get A grade in all intensive Military training tracks. They are not in the main story levels, but extra tracks which can be unlocked after finding all warp zones and completing the secret levels. Check them out here:
There are 6 intensive tracks which you can find under the bed in the main menu (the room) after completing warp zones, The good part of this is that they're not as hard as they look. I was able to get A on them after 4-5 tries. You can get A with even 17-18 fouls.
So with just a little practice and persistence you'll get them.
I'll put a video for each track for those who need some tricks and a visual guide as well.1. Vehicle Training Volume I
This one is pretty easy, just time sending your rope. Don't worry about delay when you're hanging. If you feel you're going to crash into red obstacles, just keep hanging on and control the bike to the right point. As you see in the video below, there are some errors, but still the result is much higher than A grade :)2. Elite Physical Fitness Program I
This one looks like the extreme levels of Super Meat Boy. You need to dodge many gears and jump at the right moment, so timing your jumps is very important. You should not exceed 18 fouls. Practice is the key. For me, this one was the hardest of the 6 tracks.3. Vehicle Training Volume II
This level is not about speed, it's all concentration work. If you push RT to accelerate the vehicle you need to push and release it correctly. It means you need to focus on how much to hold the RT and when to release it. The green wheel is the one which accelerates your vehicle, so it's very important to know when it should be in front and when it needs to be in back. There are some parts which you need to practice a bit to get into it.4. Weapons Training Volume I
The key is to shoot'em up before you get close to them. The only hard part of this level is the last part when a laser pad is after you and you need to hurry. Just keep in mind you can't escape the enemies, you need to shoot them and if you miss too many bullets, you're going to die. So concentrate on your shooting and jumping and you’ll be fine.
PS. after the first elevator, when you go into a room with four turrets above you, don't do what the guy in the video does. Just stay on the first platform to the right. Shoot 2 left turrets then jump one pad to the left and shoot the right ones. You can still stay on the right pad and simply shoot the torret's bubbles as well.5. Weapons Training Volume II
You need to do 2 things together here: handling your bike and shoot the buttons to access your path forward. When the laser pad is following you from behind, first try to handle your bike, and when it's stable on the path, shoot at the buttons.6. Physical Fitness Program II
This is an original platformer level like the previous one (level 2) which requires you to focus on your jumps and time them right.
Even though you can have some fouls on each track but they shouldn't be more than 17-18 and remaining time should be around 27-28 mins left.
The videos are not mine, I did much better than this guy, so you should be able to do much better, too. But credits go to youtube user: UniversityOfTrials.