Ooh, Shiny! achievement in Dead Island 2

There are 8 legendaries in the game and they're rewarded from completing a certain quest. The "easiest" one is "Emma's Wrath", since all you have to do is complete all of the main quest.

I will list all the other weapons from where you get them and with videos.
This will be formatted as

"Legendary" "Name of quest" what type of quest

"Emma's Wrath" is rewarded by completing the "Hollywood Ending" main quest (the last main quest of the game).

"Blood Rage" is rewarded by completing the "fool's gold" lost and found quest.

(Full credit to Powerpyx for the video)

"Body Count" is rewarded by completing the "[Redacted]" lost and found quest.

(Full credit to Powerpyx for the video)

"Big Shot" is rewarded by completing the "It's not your fault" side quest.

(Full credit to Gamerpillar for the video)

"Brutalizer" is rewarded by completing the "Body Art: The Unveiling" side quest.

(Full credit to Backseat Guides for the video)

"The One" is rewarded by completing the "Beacon of Hope" side quest.

(Full credit to Backseat Guides for the video)

"Krakotoa" is rewarded by completing the "Missing:Steve" lost and found quest.

(Full credit to Powerpyx for the video)

"Party Starter" is rewarded by completing the "Drunk and Disorderly" lost and found quest.

(Full credit to Powerpyx for the video)