To use these files to shortcut the Challenger achievement for Borderlands the PreSequel:
-Extract these files
-Copy them to your save folder
-This is located with a filepath such as:
C:\Users\[GamerX]\Documents\My Games\Borderlands The Pre-Sequel\WillowGame\SaveData\12345678912345678
-Rename the files to replace the X with the number that comes next in your list of save files.

When you load up the game, select the save file named Challenger (the character is Athena, Lv. 70).

Then all you need to do is complete the final Challenge to unlock the achievement!

What is the final Challenge? Check out my guide on TrueSteamAchievements to see the list of what needs done and find the one that's left.
A hint: It's so easy to do, it'll be a slide. You might even just drift on by it. So give it a whirl and enjoy your shortcut to completionist fame!