You can die and restart inbetween the kills, I did this by accident while going for ten in a row in the second part of the REVOLUTION chapter. Just enter the area and start chugging the knives repeat until the achievement pops up. Barely even human's method is good enough but I found another one on the internet. Simply load Developer Level which is located in Chapter Menu in the new mission tab( press Q). Go to shooting range and arena door > Shooting range. Near the controls on the right there is a box which you can find knifes in. Press the button on "Undead (10m)" and start throwing knifes. Some of the enemies die with two knifes, that's not a problem when you run out of knifes simply go to refill. Proceed until you get the achievement.