"Complete wave 1" is an objective in the sidequest Hyperion Slaughter: Round 2 in Borderlands 2
Walkthrough
This first wave has a large number of EXP Loaders coming at you from the East. Careful shooting will make your life a lot easier. They will always start slow then move to rush you. This is hardly a good wave for critical kills at first.
Once you are through the EXP Loaders you concern will shift over to the Combat Engineers. They are a much better target overall. You have a good dozen or so to kill off.