"Kill more enemies" is an objective in the quest A History of Simulated Violence in Digistruct peak Challenge DLC
You move into the next area of the Deprivation Depot. There you will encounter a number of Bandits, Maniac Midgets, Spitter Skags and more.
Work your way along the path. You will find more Bandits waiting for you: Marauders, Maniacs and then more Super Badass Slag Skags. Defeat them and you can move into the next area, Butcher Base.