Sniper: Ghost Warrior 2
37 Achievements
20-25h
Death's Scythe
Take 50 headshots in single player
45.0%
How to unlock the Death's Scythe achievement in Sniper: Ghost Warrior 2 - Definitive Guide
PuritanSoul
TrueAchievements
TrueAchievements
Headshots count whether they are via the sniper rifle or pistol, and also continue to count if you die and replay checkpoints. That said, there is very little need to grind this - there are 10 missions in total, with between 40-60 enemies per level, so you will probably unlock this well before halfway through your playthrough.
The only issue to mention is that on casual/medium you recieve aim assist (a red circle shows where you will hit) and as such getting headshots is straightforward. On expert you do not get this, and given the difficultly of wind/height/distance, it is often safer to go for body shots. That said, you can still get this on expert, mainly through closer range headshots (under 100m you can just aim for the head), and so you should still be able to unlock this on your first playthrough.
XniresistX
This trophy is cumulative across all playthroughs and mission selections. Unless you are playing on hard, then chances are you will have earned this trophy before the game is over. When going for a headshot make sure to empty your lungs before each kill, and make sure the target is stationary before firing. On easy or medium you are still given the bullet trajectory indication (red circle in your scope), so this is quite easy on a lower difficulty.
MeonOner, Nevander
This will come with natural progression. Continue playing the campaign and try to always aim at the head. Take your time and do not rush to take the shot. Press 
down to hold your breath.
To check your progress and kills, from the main menu select extras and personal stats.
