The Invincible

After reaching the alliance field base for the first time you will be told to follow the convoy path on your map, at the very end of the convoy path you will take a side path and into a tunnel to start this achievement.

First Area: This is the area with the 2 large robots right after exiting the first tunnel.
Niemki - Dead body at the front
MAG-03 - Main large robot in front
MAG-04 - Second large robot that's mostly buried
Hofmann - Dead body at the back
SMU-27 - Go through the smaller tunnel/path on the right side between Niemki and MAG-03, through there is the building with the name tag on the top of it. You must grab this one before proceeding with the mission as there's no return after this.

Second Area: This area is where the robot is walking in circles.
ARK-03 - The robot walking in circles, grab before Batke as this is missable.
Batke - Dead body at the other end near the metal trees, be sure to walk up to him and turn him over to get the tag on his helmet.

Third Area: This is the area you go to after the robot shoots a hole through the wall and chooses not to kill you.
SMU-88 - First vehicle buried in front right after going through the hole.
Sokolny - Inside the same vehicle as above, look through the broken glass dome top.
ATR-12 - The vehicle further along with the body sitting inside.
Dobrov - The dead body inside the ATR-12 vehicle.
Osterhas - Dead body to the left of the damaged transporter
TMU-85 - This is the damaged transporter itself, you can see the black plants growing on the top of it.
ARK-16 - Inside the damaged transporter at the back of the dark room, clickable after opening the door and throwing in the flare.
LMU-54 - The last vehicle buried next to the giant shield just past the damaged transporter.

Final Area: This is both the side path leading to the shielded area and the main shielded area itself.
FTP-02 - This is the drone we encounter on the way through the side path, can't be missed and will automatically mark for us so no need to click it.
Mierwa - Dead body found along the side path just after the drone.
TMU-88 - Large active vehicle waiting for us to board on the left as we exit the side path.
Stelinak - Dead body towards the back of the area buried in the sand.
EBT-05 - This is the vehicle we enter to drop the shield, this will auto mark on the list.
Antke - Inside the vehicle that we use to drop the shield is a helmet, click that for the final person on the list.

If you need more help with this you can follow m video guide below:

Here's my video guide for this one.
Be sure to ride straight to convoy. Don't take a shortcut.

Here's a full video guide showing all the pieces and location. You cannot take the side path, if you do you miss a collectible