80s Hero Achievement
DLC Vietnam: Complete the game in Action Movie Mode (Host only).
Once you have completed Hours of Darkness, you will unlock Action Movie Mode. In the Main Menu, launch the add-on and select this difficulty. Action Movie Mode allows you to carry up to four weapons, additional resources, and call in airstrikes without the need to destroy AA guns.
Much like the "Roguelike" achievement, there is no set way to go about this playthrough. You can take the time to complete every objective and explore the jungle thoroughly now that you have a surplus of resources, or you can just make a beeline sprint to the extraction zone right from the start. It really doesn't matter how go about it, and since this will likely be your second or third playthrough, a speedrun of sorts might be in your interest.
Regardless of how you approach this Rambo-inspired mode, the achievement will unlock once you escape the jungle and the credits begin to roll.