Achievement 'Elf Bane' worth 10 Gamerscore.
This achievement is very easy to obtain, because most people play as elves and they are the easiest race to kill for they have the lowest amount of life.
The pistol is a 3 hit kill on an elf if a headshot is involved, same with the rifle. A good way to get a quick kill is the shotgun. It is a one hit kill at around 5 feet away. I wouldn't recommend using a rocket launcher or a minigun against them, for they can teleport away before you have the chance to hit them.
The things you must watch out for when going up against elves...
*Elves are the only race in the game to regenerate life without the need for a Tree of Life. So, if you damage them and they teleport away before you had the chance to land the last hit, the next time you meet them they could very well be at full life.
*Elves almost always have teleport, so always try for that quick kill before they have the chance to use it.
*Elves are sneaky. Always going for the katana bleedout kill, so always watch your back, especially if you are a troll.