Positive votes for the other solutions! But I found this method the easiest so far!
-Play Episode III, Chapter 4 - Defense of Kashyyyk in Free Play (also possible in Story).
-Pass the beach area when you lower the tall wooden door. Enter the area with the downed ARC fighter in the mud.
-DO NOT KILL THE TWO BATTLE DROID COMMANDERS ON THE LEDGES. They will keep calling in for and endless supply of Battle Droid Reinforcements. I'm pretty sure there's is around 10 or more Battle Droids that try to surround you.
-Do your Jedi slam. Cheevo unlocked! If you mess up, you can just wait for the commanders to call in for reinforcements again and again.
-*Bonus Tip* I would suggest to use a ghost character or use invincibility so that your character won't take damage while your trying to get the cheev. If you don't have those just switch to a droid (the Battle Droids won't attack you and will surround you), then quickly change to a lightsaber character. Slam and EZ Cheevy!
(Credits to risseless' Fire in the hole! solution! Positive votes!)