This is one of the secret cheevo's and is called THE FORCE IS WITH YOU and it is awarded for completing any level with out dying and not using an invincibility cheat.
Ok this is actually a very easy cheevo to get.
I got this on the mission JEDI CRASH, count dooku mission 3.
This mission sees you flying from one point to the next and taking out a few targets with proton torpedos.
There are very little enemies and what enemies there are can be avoided. when on foot if you do fight any1 just keep your lightsaber attacking to deflect any shots.
This level can be done in less than 10mins with minimum of fuss.
If needed you can also use the regenerate hearts cheat which can either be obtained by finding the red brick or putting the code in (which i wont put here but can be found in other solutions) not that you should need it as this level is very very easy.
See my guide for full break down of the level.