Warhammer: Vermintide 2

For this achievement, you have to use the upgrade altar that has the hammer and anvil symbol floating over it. These typically appear once or twice a mission, and you can choose to upgrade your melee or ranged weapon here. If this is one of your last achievements, I suggest playing on a lower difficulty and saving all your coins for when you pass by one of these altars. The highest rarity it can go is red, so don't exchange your starting weapons as everytime you do that, it automatically increases the rarity of said items. If you're playing on Recruit or Veteran it doesn't really matter, they're very easy to complete with any weapon you use.