Here is the full list of all 21 Elven Assassin achievements.
10K KilledOrcs
1K WindowShots
50K Fired Arrows
2.5K HeadShots
2.5K KilledOrcs
20K Fired Arrows
500 HeadShots
100 WindowShots
50 Window Shots
500 KilledOrcs
5K Fired Arrows
50 Head Shots
1K Fired Arrows
50 Orcs Killed
100 Fired Arrows
10K HeadShots
25K HeadShots
50K HeadShots
25K KilledOrcs
50K KilledOrcs
20K WindowShots