This will complete every single area specific challenge, DLC included. That's 168 total. (Complete list at the bottom)
This works for Xbox/PS3/PC and all charcter classes.
If you haven't already discovered the area or challenge they will complete automatically when you do.
This will not affect any of your other completed challenges.
1. Open your desired save in Gibbed's Save Editor.
2. Go to the "Raw" tab.
3. Scroll down to "LevelChallengeUnlocks" and click "(Collection)" next to it.
4. Copy the complete list of numbers in the spoiler below and paste it in the box.
Note: If there are already numbers present here delete them.
5. Scroll down to "OneOffLevelChallengeCompletion" and click "(Collection)" next to it.
6. Copy the numbers in the spoiler below that correspond to each of the four "OneOffLevelChallengeData" options in the left column and paste it in the "("Collection)" on the right side.
6a. Main Game - ContentID - 0 PackageID - 0
6b. DLC 1 - ContentID - 1 PackageID - 1
6c. DLC 2 - ContentID - 1 PackageID - 3
6d. DLC 3 - ContentID - 1 PackageID - 4
Note: If these aren't already present you can't create them from scratch because the editor will give you an error similar to what happens when you try to add mission data manually. For these to be there you must have completed at least one area specific challenge from that particular part of the game. I used new characters during testing so I figured out which challenge was easiest for each one.
Main Game - This Aint My First Rodeo
DLC 1 - Skiffless
DLC 2 - I Can Fly!
DLC 3 - Power High
7. Save your game and enjoy.
Here's a list of all challenges that will be completed.