Hyper Light Drifter

Before you attempt this achievement, I would suggest doing "Hoarder" so that you have all the weapons, and enough cash to buy all the upgrades. You'll also have all the outfits and can equip a few items to help (I would suggest Blue, Fuchsia, and Orange). The outfits don't help a ton, but you'll need every little bit of an edge. You'll also need at least 12 keys, as the Horde rooms are down an elevator in town past a key door.

Once you get past the door, head down the elevator and you'll need to complete five total challenges. The first four represent the different zones of the game and you'll face the same enemies you would in those zones. The final challenge is a mixture of all the enemies from the game. Having already beat the game, you'll be familiar with all the enemy attacks.

This playlist has videos of each of the five rooms.