There has been some confusion on how to obtain this achievement. Yes, although the steps for unlocking the achievement require either playing with a Borderlands Developer (very unlikely to do nowadays) or playing with someone who has the achievement unlocked. However, there is an additional step not many are aware of where you must play with someone who got the achievement WITHIN THE SPAN OF NO MORE THAN 1 YEAR.

For example:
I unlocked this achievement January 12, 2023
I will be able to help others unlock the achievement anytime until January 12, 2024

The achievement unlocks as soon as I or your friend join your game, no additional steps are required.

Now, if you're not able to obtain this achievement with anyone, you've come to the right place!

If you'd like help with this achievement please do the following:

1. Ask me in the comments and send me a friend request on Steam and I'll get back to you as soon as possible via Steam Messages.
2. We'll arrange a time that works for the both of us (I almost always respond within 24 hours)
3. I'll join your game and you'll be granted the achievement :D