Call of Duty: Advanced Warfare

This achievement is best done during the first infection round as enemies are easier to gather where you want them. To unlock the achievement you need to gather 5+ host/infected zombies in the decontamination area (a marker will come up on your HUD during the infection round to guide you to it) then activate the pad (by pressing ) while they are running across and around it. The host/infected zombies are the ones with green gas coming out of them, the ones who 'infect' you when they land a hit on you. Not to be confused with the acid zombies who, unsurprisingly, leak acid.
Here is a short capture of the moment I unlocked the achievement. Although the achievement doesn't show on the video (due to Upload Studio not showing the overlay) this is the moment it happened:
Thanks, and happy unlocking.

Also see my thread in the forum in regards to the Easter Egg hunt (music and main) and the steps I've unlocked - New Easter Egg on Infection

I have created a video of me getting this achievement and the best way to do it.

First of kill a few zombies for points to open the next area.

I choose to go through the entrance next to EXO medic because you have a bit more space outside at the petrol station, other than that it really does not matter which side you take since the doors still cost the same.

Once you have gathered enough points (1,500) open Value Voltage (next to EXO medic),
buy a weapon if you feel the need to then open the gate to the sewers (2,000) which is just next to the starting area building you just came out of and down a hill of debris.

Once done head straight forward, turn right then turn 90 degrees Anti-clockwise to require your EXO suit.

The 'Pit' which is what your looking for is beneath the EXO suit near the Gator-trap, the map makes this look a little confusing at this point, but as long as you follow the path in the video you will get there.

Now just wait until round 8 (or 7) for the Host zombie round to spawn, when it does you will hear a transmission warning you that this is a boss round. The Host zombies are the zombies that emit green clouds from there model and when they land a hit on a player that player will have 60 seconds to cleanse themselves until death, not to be confused by the acid zombies that look extremely alike, either way it really isn't that much of a hassle.

Once the infection round takes effect run back to the pit I mentioned earlier and surround yourself on the pad with the Host zombies after you, try to take a few hits until you are completely surrounded but keep an eye on your meter, each hit from a host zombie reduces your time by five seconds!

Once comfortable and ready to start hit the decontamination zone by holding (cost 250 points).

Then that should be it, the achievement will unlock as soon as the requirements meet, hope this helps!

Video guide:

Here is my video guide for scooping up this cheevo!