Headshot Every Type of Enemy
This trophy requires you to kill all 9 enemy types with a headshot. These enemies are:


Foot Soldiers - The normal enemies in red armour.
Berserker - The normal enemies who run up to you with a Shotgun.
Molotox Striker - The normal enemies who throw fire bombs at you.
Heavy Gunner - The heavily armoured enemies who are carrying Terror 4000 Miniguns.
Heavy Flamer - The heavily armoured enemies who are carrying Flamethrowers.
Sniper - The enemies with pointed helmets who snipe you with red targetting beams.
Running Dead - Melee - The zombified scientists encountered near the end of the game that attack you with neon knives.
Running Dead - Shotgun - The zombified scientists encountered near the end of the game that attack you with shotguns.
Running Dead - Molotox - The zombified scientists encountered near the end of the game that attack you with fire bombs.
It is highly recommend you unlock this trophy during your story playthrough, as the "Heavy" enemies spawn extremely rarely post-game. There are plenty of chances to get this during the main story though, so don't worry too much about it. The best way to achieve a headshot is to use either the Kobracon (Sniper Rifle) or Fazertron (Assault Rifle).