I personally did this during level 11
”Apokolips, Wow”*** Spoiler - click to reveal ***This level is very short compared to the rest of the other levels, and half of it is aboard a large shooting tank.
As soon as you board the tank and take control of the gun shooting with 
, there will be the following:
2 enemies fly in from right to left near the screen
2 enemies fly in from left to right at the rear of the screen
2 with a 3rd on the bridge in the central part of the screen
Now just aim with your analogue stick(s), and then shoot with the button killing all the enemies.
You will slowly go up from a x1 combat multiplier to a x10.
Only shoot the enemies not the gold debris to progress in the mission otherwise you’ll lose your multiplier.
As soon as you hit the x10 multiplier you’ll hear that magic pop, achievement unlocked.
Congratulations!
Happy Hunting
A Few Other LocationsHub quest Planti - Social once you reach the last section of enemies to kill.
Level 12 - Boss Fight Section This is against Kalibak & his T - Rex Mech just keep & hitting the waves of his enemies attacking you. Then you can hit him as well if struggling for time/enemies to spawn in but do not kill him before you get your x10.