Horizon Zero Dawn
79 Achievements
62-78h
Stealth killed 10 machines
Performed a stealth kill on 10 machines.
55.8%
How to unlock the Stealth killed 10 machines achievement in Horizon Zero Dawn - Definitive Guide
Wayens
TrueTrophies
TrueTrophies
Stealth Strike is one of the first ones you can unlock.
Buy it with 1 skill point.
And now when you hide in tall grass or sneak up behind a machine, a prompt for that skill will appear.
Activate that skill and stealth strike your target.
Watchers are the ones that can be killed in one strike so easiest way is to stealth strike 10 Watchers and you should see this trophy pop.
Have fun!
CRSlater
TrueTrophies
TrueTrophies
Blaze, Naruto, Shippuden, PowerPyx, RemingtonI
Skill Required: Silent Strike
You must first purchase and learn the skill called "Silent Strike" from the Prowler Skill Tree. This skill costs 1 Skill Point and when you sneak up or stealth behind enemies, press 
to perform a silent takedown which results in an instant kill on small machines and humans. If this move is used on medium sized enemies, it will only deal high damage.
For the trophy, you need to use the "Silent Strike" to stealth kill 10 machines in order for this trophy to unlock. You can easily unlock this trophy by hiding in tall grass and luring machines like Watchers or Striders to your location by throwing rocks or using the Lure Call skill to lure a single enemy to your position. When the machine is close enough to perform the Silent Strike, press to kill it. Remember, this works best on the weak small machines with little health. Once you've performed your 10th Silent Strike kill, the trophy will unlock. Stats can be tracked by going to the Notebook and viewing "Statistics".
It should be noted that “Strike from Above” kills will also count towards this trophy's unlocking.