A Guide to Help those who have experienced the “Buggy” aspect of trying to get this achievement… I may have a solution!
What to Do
Start the level, even in “Mission Replay”. I played the Mission on Normal just to get it over with, but feel free to do whatever you want.
Weapons you will find (be sure to scan the rooms):
- AR (MA40)
- Sidekick (MK 50)
- BR (BR55)
- Hydra (This can be hard to find)
- Plasma Pistol
- Pulse Carbine
- Plasma Cannon
There are also Grenades:
Which you will need to get kills with too. I do not believe that they have to be sticks, in the case of Plasma and Spike ‘nades. Same goes for Knives on the weapons like the Mangler and Ravager (or Needle Melee with the needler).
I would only say be careful with the Hydra location as it is literally at the end of the mission after you play platformer across the falling boxes (I guess are “Drop Ships”), in the last room where a bunch of enemies on top of that room will get blown up out of convenience… you will find it on the LEFT SIDE (when entering the room) if you scan the room you can’t miss it.
Other than that… there is one BUG issue I encountered. I often play with Catch, IWHBYD and Grunt Birthday Party on, that’s how I have played since Halo 3 back in ’07.
I found that when I disabled the skulls, I got the achievement, cause I tried 6 times in a row to see what was happening. SO, if you have Skulls On, Be sure to disable any skulls you might have turned on if you do play with them like I do.