Spoilery Spoiling Spoilers Ahead!
*** Spoiler - click to reveal ***The second toughest of your four new targets is the Hyena who hides out in Giza.
After investigating her lair (don't forget the dude in the cage and the hyena in another cage)
you are directed to a tomb under the pyramid with the synch point.
Run through the tomb, and she confronts you before running outside. Careful as she has oil traps set and fiery arrows to burn you. Get outside and you get a fight in a sandstorm.
Just follow where her arrows are coming from, use a large weapon for max dmg per swing,
and if you can use your overpower on her. This is because after she loses about 1/4 of her health she throws another smoke bomb and runs, but not if you cut through all her health in one shot!
As always she will have a death cutscene, once it is done the achievement shall be yours!
Let's keep cheevin' Together!
EDIT: Thanks to decaying dead for his comment. There is a moment where you exit into a sandstorm and a cut-scene follows. Or it should at least, he and likely others have experienced no cut-scene and therefore cannot finish the mission. If this happens you will have to reset the game.