Perform 1000 melee kills. The quickest way to get this achievement, is to set up a match with the following settings:
Map Size: Small
Bots: 15 (Agent/Bully)
Time Limit: None
Point Limit: 100
Weapons: Custom (Shields in five slots, Viblade in sixth)
Grab the Viblade as soon as possible. It will spawn on a balcony above one of the arches. Since the enemy AI is set to Bully, they will focus on the player with the least kills. If that's not you, they will be oblivious to your presence. Hit them in the back... Once you have reached the score limit, set up 9 more matches with the same settings until you have the 1000 melee kills. It will take a couple of hours. It can be a mix of online and offline.
If you own a second controller, you can get your kills even quicker. The mode needs to be switched to Team Killcount. Change the bot count to 14, to allow for your second controller. Set it to "Bots vs Humans". When the game begins, take your second controller around the outskirts of the map until you see a rock which you can climb on. If you are facing the Viblade spawn, it is 45 degree's to your right.
All the bots will swarm to the rock, but will be unable to hit the second player. This makes them easy prey.
Note: Melee kills from behind only count when using the Viblade. When using any other weapon, you must hit them from the front.
*You must complete the match for your achievement progress to register.