Back 4 Blood

[Guide]

After struggling for a while to get a legendary to drop (it only dropped green stuff for me). I found a more or less reliable way to get this. Legendary weapons only appear in the white weapon chests that are found in hives. The amount and locations of these chests is random.

Load up solo mode: recruit

1. First you want to play Act 3-1 (Farther Afield) with a speedrun build. This one has at least 3 potential hive entrances that I know of
2. One is after the cornfield in the left corner, behind a flatbed. The 2nd one is after passing through the house, immediately on the right next to the side of the house. The final one is immediately next to the saferoom door (can't miss it)

3. After passing through the hives you should find yourself the entrance to the Inner Hive "the nursery" (random chance that it spawns). It glows red. (you may have to rinse and repeat steps 1-3 untill you get lucky)

4. In the nursery you are guaranteed 2 white chests
5. Open these. If a legendary weapon drops. Great. Grab the C4 and open one of the webholes. Kill any zombie (special or normal doesn't matter) and the achievement should pop
6. If not. Simply quit out and go back to your save. You should be able to reload back in the nursery and the chests should be there again
7. Rinse & repeat untill legendary drops

Note: It's worth noting I did this by entering the hive in Act 3-1 and only had green weapons equipped when I was opening the chests. It is unconfirmed if legendary drop rates get better once you proceed further into the act.

Now, at this point you have the achievement but if you happen to finish the Nursery section you will carry this weapon into the next mission. You are able to quit the game entirely now, load up online play instead of solo and then continue this save.

This allows you to drop the weapon for your friends to make their achievement effort much easier.

UPDATE:
- The new cleaner named 'Tala' has a perk that allows warped chests to spawn in each map. That means it is now possible to get this achievement outside a hive, as long as you have a Tala on your team.
- In addition to that, the droprate of legendary weapons seems to have significantly increased. Achievement might be very viable to get during normal play if you have a Tala on your team.

I had a lot of trouble getting this achievement until I found a strategy that actually worked for me. I spent many hours farming the checkpoint in The Nursery where there are 2 Warped Chests. Every time I would open a chest, I was only getting green weapons. On each attempt, I only had a green or white weapon equipped myself. I spent about 3 hours doing this with no success. I decided to try doing a hive in a later Act. I chose Act 2 - Heralds Of The Worm Part 2. On this attempt, I already had a purple weapon equipped. There is a Hive spawn off to the left immediately after exiting the saferoom. The first Warped Chest I found in the hive had a Legendary weapon in it. I believe that having a purple (or blue) weapon equipped significantly increases the chance of getting a Legendary from the chest.

I am aware of one other person on TA who had the same problem as me, then once they had a blue weapon equipped, they got a legendary from the first Warped Chest they opened. I hope this helps others. This achievement was driving me nuts until I found this method.