SUPERHOT

You need 1500 kills to unlock the last endless level (PWRPLANT) and out of these 1500 kills, there need to be 150 kills in each level to unlock all 4 different types of the endless level.

There are 9 different levels called LAB#18, STAIRS, BRIDGE, BREAKIN, HALL, LOBBY, WAREHAUS, OFFICE, PWRPLANT each has 4 different modes. Endless, Race, Time and Real.

Endless: The mode you will be playing in, just killing red dudes.

Race: Get 30 kills as fast as possible.

Time: Kill as many red dudes as you can in 20 seconds of in gametime. (Think SPEEDRUN)

Real: Kill as many red dudes as you can in 60 seconds of real life time. (Think SPEEDRUNrt)

Every 50 kills unlocks the next one. See the text and video guides below for strategies on each individual level.

LAB#18
There is no clear strategy for this one, just play how you would normally play. Pick up guns when possible, use katanas when possible as they are the only melee weapon that does not break and jump to evade bullets. A good warm up to endless mode.

STAIRS
This is the same map as 26STAIRS. Run to the top level of the stairs and wait around the corner, picking up the red dudes' guns whenever possible.


BRIDGE
As you spawn in a different place each time, there are no directions that can be given. Just follow the video to that corner and wait there for the red dudes. Perfect spot for a katana.


BREAKIN
This is the same map as 11BREAK. What you want to do it go in the hallway beside the glass room and wait around the corner, preferably with a katana.


HALL
Again, sadly there are no tips and tricks for this map. Just play to the best of your ability and rejoice, you are halfway there.

LOBBY
This is the same map as 31LOBBY. Go to the right off the beginning and wait around the farthest corner (if at the main spawn). The red dudes will only ever come from the side you just came from. If the red dudes are not coming try stepping out and breaking the other pane of glass.


WAREHAUS
There is a hallway on one side of the map which stretches across the entire length of the map. Run back and forth in this hallway picking up new guns as much as possible.


OFFICE
This is the same map as 27OFFICE. You will spawn in a different spot every time, so no use giving directions. But try to find the elevator and sit around the corner to the right. Get a katana as soon as possible.


PWRPLANT
The last level, and fittingly no strategy again. Nowhere to camp or wait around a corner. Just play how you would normally play and feel good about finally getting this achievement done.

(I know it says I dont have this achievement, but I have it preloaded)

To try to put this as succintly as possible:

1. Complete the campaign to unlock Endless mode.

2. There are nine Endless rooms, with four Endless modes per room. When you unlock a room, only the first mode is unlocked. You need 150 kills in that room to unlock the other three modes. It isn't required that you play or complete all four modes, only that you unlock them. You can get your 150 total kills per room on any of the modes you've already unlocked.

3. You need 1500 kills on the first eight rooms to unlock the ninth room, plus 150 more to unlock all four modes of the ninth room. Once you have done that, the achievement will unlock the next time you return to the main menu.

To summarize:
1200 kills (8 x 150) to unlock all four modes of the first eight rooms, PLUS
300 more kills in any room to unlock the ninth room, PLUS
150 kills in the ninth room to unlock the four modes of that room
--------
1650 kills to unlock the achievement

After you've unlocked this achievement, continue grinding 337 more kills in any room to unlock:

This, along with the "Can't get enough" achievement, isn't hard, it's just a bit tedious.

The katana is your best friend. It does not break like other melee weapons and you never run out of ammo. Almost all of the endless maps offer some kind of enclosed space or corridor where you can hide and wait for enemies to arrive.

The following video is demonstrating this in the "Office" map. There's an elevator, just keep pushing towards the wall slowly and smash anyone coming in.