Note: This is actually done on level 9, but on Level Select it is Level 8.
This is obtained on Level 8: The Return (Kamino)
After you cross the broken bridge and meet up with Kota, you will take an elevator. In the beginning of the level near two rifle imperials you will see a lightning tower. Force lightning () the lightning tower and the tower will then shock the Rifle Imperials nearby. You may have to do it several times for them to die. Now continue on and jump over the ledge where you will meet two AT-MPs. Kill them and continue on again.
Go around the circular platform and you will encounter a decent amount of storm troopers. Do NOT kill the storm troopers. Instead, continue on down the path and you will see another lightning tower. If you take a few steps past it, more enemies will come at you. Stand near the lightning tower so the storm troopers will come towards you. If the Terror giants and AT-MPs are bothering you, then kill them. When the storm troopers are near the tower, Force lightning it over and over until all of them are dead. If the achievement doesn't unlock because you don't have enough kills, kill yourself and do it again.