Hitting at least 3 enemies with an attack, increases your damage by 24-36% for 3 seconds.
Hitting at least 3 enemies with an attack, increases your cleave by 140-200% for 2 seconds.
3.5-5% Critical Chance on Weak Spot Hit until your next Critical Hit. Stacks 5 times.
5-6.5% Strength for 3.5s on Close Range Kill.
This is a Malice build because it's the lowest difficulty to get this achievement on. Malice also has a tendency for players doing weird stuff so it make take a few tries. I was able to do it on the train assassination mission with a random speed runner knife zealot. He took the aggro very effectively even if he did go down a couple times.
The Melee weapon doesn't matter too much the main thing is to be able to be so far away that you wont need it.
I prefer the recon as its a laz gun so you can get free bullets every now and then but more importantly you can just spray down a horde to prevent it from getting close.
The playstyle is to lag slightly behind the group and always pop stealth when a horde spawns. During the first event hide directly next to the "Death Before Dishonour [sic]" dumpster. Run in to do the button press and give covering fire but generally you are hiding. At the end hide in the elevator and shoot across the map.
Might take a few tries good luck.