Go to the Oni sword base level and turn on the cowbell skull. This will amplify splash damage. You can use this on any difficulty except easy and also need to turn on team scoring.

Ignore all the enemies you see and run to the locator, pick it up and then aim it back toward the enemies.

Call in the strike and then crouch back behind the gun case. This will give you a check point before the locator gets fired off.

Once that happens, press start and then go back to the last checkpoint.

You should then see the Covenant getting destroyed and you don't need to fire off the locator again!

Then simply keep going back to the last checkpoint you saved!