Hello internet
This is a DLC story based achievement that is extremely hard to miss, you can only miss him if you start the DLC and then immediatly leave. It is the first ''boss'' of the DLC Tiny Tina's assault on Dragons keep. After you enter the unassuming docks keep walking over the sandbar and you will find him. He is accompanied by several skelletons but isnt very hard to beat.
if you downvote please let me know why so i can change it in the solution.