For this Achievement you have to kill 7500 enemies in total.
After completing the story I was at around 6000 from 7500 kills.
Keep in mind that for the Achievement Hitting the Jackpot you have to kill 1000 enemies within expeditions.
I killed 1000 enemies in expiditions and farmed up the missing ones by doing the following "strategy":
Load up story point at the first city (world tier 1) —> checkpoint: reach across the river
Follow the path and don't kill any enemies. A lot of them will spawn and run behind you. Now you can kill around 25-35 at once. New enemies will spawn 2-3 times doing so and you can just run a few circles to collect them behind you and kill them again. Press Start-Button, go to main menu and reload the same checkpoint again. You can do this over and over again until you get most of the Accolade Levels covered like kill x enemies with certain weapons or use a skills x times.
Note: Loading up a certain story point will override your current save but you can always select all story points and checkpoints in the main menu. That means you don't have to complete the story again to jump to a further point in the story (e.g. if you are missing a mission or something else).