To provide a bit of clarity, here is a more detailed explanation of what you need to do, how to do it and how to avoid doing more than you absolutely have to do.
Couple of points:
- Do not shoot any jackals unless you absolutely have to kill them
- In fact, do not shot unless it is to kill the gold elites or to survive an area. If a stray bullets hits the shields of a jackal, you will most likely have to restart the mission.
- Grenades are your friends
- Marines are not your friends (for this mission!)
- Minimalism is a good rule of thumb for this mission
Alright, here is a quick walkthrough for this mission:
1) Pick up the stealth armor ability that is located behind the Hornet.
2) Kill the two jackals that are just north by northwest of the spawn. The assault rifle tends to work better to take down the shields of the jackals more quickly.
3) There is an unmanned turret to the south of your spawn point. More importantly, there are a couple of explosive barrels on the east side of the area
where you will encounter two more jackals. Dispatch the two jackals with your assault rifle, and then walk over to where the barrels are located.** You may have to do some maneuvering to get the two marines to stand next to the barrels.
4) Once they are there, just shoot the barrels and that should leave the marines 3-5 hits from death. Walk out in front of the unmanned turret and the marines should follow. Then just slide in behind them and the turret should finish them off. In other words, position the marine between you and the unmanned turret.
5) The mission should now be significantly simplified and shorter without those two marines. Kill the gold elite around the unmanned turret and the three grunts. (1/6)
6) Head back up the path you came, and activate your armor ability when you find the two or three suicide grunts. Head north and then north by northwest. Ignore the jackals in the trees
. You should find a small alcove with a couple sets of exploding barrels and another gold elite, four grunts and a suicide grunt. Grenade the gold elite (2/6)
7) Active your stealth armor ability, and head a bit south, and you should find a manned turret,2 jackals, and another gold elite. Take out the two jackals first, then hit the turret and elite with one of the grenades. (3/6)
8) Head back to the original spawn point with your stealth armor ability activated. There will be a manned turret northwest from the spawn point, a gold elite and 6 grunts.
9) Make sure you activate your stealth armor ability right about where the bodies of the two jackals that you killed at the beginning of the mission. You will want to move quickly through the area with the manned turret and tag the gold elite with a sticky grenade while you are invisible. (4/6)
10) Proceed to the south, and follow the trail to the next elite. If you can hug the west side of the map, and skip this elite, you can move right along to the last elite in the far northwest corner of the map. Tag him with a sticky grenade (if you don't have one, there is a bin with 3 sticky grenades right by the last gold elite). (5/6)
11) Most likely you will need to wait for the armor ability to recharge. Let it recharge while essentially hiding at the edge of the map.
12) Once the armor ability is charged, head back the way you came, and make sure not to fire your gun. There will at least 5 grunt majors (silver grunts), 3 suicide grunts and 6 jackals. If you hit the jackals shields and don't kill them, I'm pretty sure that will fail to fulfill the requirements for this achievement. Instead, again, sticky grenade the elite (6/6)
13) Utilize the stealth armor ability and get the hell out of dodge. Head to the Hornet and end the mission, where your achievement should pop. Do not fire your weapon for any reason, or toss random grenades.
If you have any feedback, please let me know! I'll try to answer any questions anyone has!
P.S. if all else fails, buy rockets + damage boost and blow everything up. That works too