Dead Island 2

To get this achievement, you need to earn yourself a Superior weapon, which is the purple rarity weapons in the game. The earliest Superior weapon I got was Peggy from the Curtis questline, but as you level up they become more common. You'll then need to apply a Mod and 3 Perks to your Superior weapon, so choose your favorite ones and it should pop up.

Note: I have heard that this achievement can be buggy at times and not show up when you do fully customize your weapon. You can remove Mod/Perks from your weapons, so long as it isn't a unique weapon that has fixed ones on it. By the time you finish the main story, you should have this achievement completed. If your achievement does bug out and you have to do some specific things to fix it, please let me know and I'll update this so others can try it.

This will probably come while playing, BUT if your in a rush to get this by the time you hit the beach area they can appear in shops. They are around 10k usually and the mods will be anywhere from 500-1500 each depending what you put on them. So around 11-12k needed if you want to take this route

*You will need a Fuse to access this location I mention*

I, personally, found this to be unlockable after reaching the beach. Once inside the lighthouse, continue on the ground floor past the stairs. Use the fuse to open the door to the corrosive zone. Once in there, take a right and crouch under the fallen shelving.

In the zombie-proof box on the ground should be a Superior weapon.

Pick it up and take it up the stairs of the lighthouse where there is a workbench where you can craft and apply a mod or perk in every slot.

You might want to save up materials and cash to afford the 3 perks and 1 mod but overall, just playing the game normally, I had more than enough to fully customize this Superior weapon.