Walkthrough to get the There's No Such Thing As Luck achievement, select arena mode in solo, either on the 2nd or 3rd wave (it's random) you'll get the mission to kill the archers. Stay near the archers without killing any enemy, when they shoot you an arrow make a perfect block to kill an enemy. If you have any doubts please don't forget to ask. Thank you.

Can also be earned during the Campaign in Chapter 3 after you take the beachhead. It takes a good couple of attempts but keep deflecting the arrow eventually you will get it just be patient and it will happen