VCI Guards
From WikiRaider
The VCI guards first appear in The 13th Floor and are one of the most dangerous enemies in the game.
Since they are heavily armored, the guards will only die if shot in the head, as Lara discovers later. Zip also gives her a clue- "That face ain't got armor on it, right? Well, that's how you're gonna have to do it." The weapons used by the guards are extremely powerful since only two shots can kill Lara.