- Find a save station and make a hard save
- Craft the Swede (the large, two handed axe)
- Fully upgrade all four categories to level 4 (Blade, Crushing Blow, Grip, and Cartridge Gun)
Easiest done when you've made some progress and amassed a good amount of materials/weapons, as a few of the upgrades may seem costly. Take note that you can disassemble your other weapons from the storage section of the computer to fund the upgrades for your Swede if you are lacking.
I recommend making a hard save and doing this in one go, not over multiple playing sessions, as many of the achievements have issues tracking your progress once you quit out of the game. This does not seem to work with ranged weapons, either, and I was only able to unlock it once I attempted with the Swede. I assume it's because you cannot upgrade the aiming devices for ranged weapons.