Far Cry 3 Blood Dragon

Kill every type of enemy with a headshot.

This is missable because there are enemies encountered during the 5th, 6th and 7th missions which cannot be found in the open world and you cannot repeat those missions without reloading a save or restarting the entire campaign. All the required enemies are humanoid- in fact cyborgs, no animals are counted, and they are distinguished by the types of weapons they carry.

The following enemies will be encountered throughout the open world and during many side-missions. Simply aim for their head with the Kobracon, A.J.M., Fazertron, Terror 4000, or Galleria 1991 and keep shooting, even through armour, until it says in the top left corner 'Headshot'.


From left to right in picture:
> Omega Flamethrower - Flamer
> Omega Pyro - Molotox
> Omega Foot Soldier - Fazertron Assault Rifle
> Omega Sniper - Kobracon Sniper Rifle
> Omega Heavy - Terror 4000 Minigun
Also not pictured is the:
> Omega Close Range - Galleria Shotgun
You can spot these close range troops as they have a 'lightning / Close Range' symbol above their heads when using Cyber-Eye.

You also need headshots on the Elite variants of these cyborgs. You will encounter three of these types of cyborgs during the Predator Side missions as your main target. You can tell an Elite variant from a normal ones because the Elites are bright neon yellow and the symbol above their heads with Cyber-Eye active is also yellow. If you miss the headshot during the Side-mission you can repeat the side-missions later by going into Options, Gameplay, then Reset Garrisons, to reset ALL the Garrisons on the map. I don't advise this however as you will encounter many of these Elite variants during the final mission so don't worry if you missed some:

> Elite Omega Flamethrower - Flamer
> Elite Omega Foot Soldier - Advanced Fazertron Assault Rifle
> Elite Omega Pyro - Molotox
> Elite Omega Sniper - Advanced Kobracon Sniper Rifle
> Elite Omega Heavy - Advanced Terror 4000 Minigun
> Elite Omega Close Range - Advanced Galleria Shotgun

During the 5th Main mission (incidentally not your 5th side mission), you will see undead scientists in green glowing chambers, these are known as 'Running Dead'. Shoot the glass to unleash them, then headshot them, don't worry if you don't get one now you will certainly get a lot during the 6th mission:


> Running Dead Melee - Machete

During the 6th mission you will encounter hoards of the previous type of Running Dead mixed with two new types, to ensure you get the achievement make sure you get a headshot on all three types:

> Running Dead Close Range - Galleria Shotgun
> Running Dead Pyro - Molotox

The 7th and final mission is the only place to find the last type of enemy. They look like Omega Foot Soldiers but are different in that they have Rocket Launchers. There is one up on your left immediately after breaching the large gate at the start:

> Omega Rocket Troop - Rocket Launcher
(*You do not need an Elite variant of the Rocket Troop)

Upon killing your final enemy with a headshot the achievement should pop immediately.

Don't forget to upvote if this solution helped any, and don't hesitate to PM me or comment with any questions no matter how trivial, nice one.

Having just finished the game and getting the achievement on the final mission, you must kill the following, and their elite variants with headshots:

Cyborgs carrying shotguns
Cyborg Snipers
Cyborgs carrying Assault Rifles
Cyborg Molotoxers
Cyborgs with Armour and Heavy Weapons
Cyborgs with Flamethrowers
Cyborgs with Rocket Launchers
Both Running Dead variants, melee and assault.

(These last Running Dead two can be found in the 6th mission where you start with a pistol and move on to shotgun, followed by sniper, etc. You'll know which mission it is because it'll advise you that you can't turn back after initiating the mission.)

You can kill each elite variant whilst performing the side missions.

The rocket launcher cyborg was the last one I got on the last level, right after destroying the base door with the KillStar, though I had seen him before and obviously missed the headshot. He's up and to the left if that helps.

this is a missable achievement unless you like to aim for the face. You'll get this at the end of the game in the Mortal Kombat type arena unless you somehow miss the hints to shoot the dead in the head.

There are 8 types of enemies.
Cyborg Rifle men,
Cyborg Shotgunners,
Cyborg Molotox throwers,
Cyborg Snipers,
Cyborg Heavy Weapons Guy,
Cyborg Pyro,
Running Dead melee
Running Dead Rifle men.

The Running Dead only appear in the final 2 missions of the story. One of them you have to shoot them out of medical tubes that glow green in the underground base. Those only spawn the melee versions. In the final level where you have to kill a ton of enemies in the MK style arena is where you'll find the rifle men.