Yub Yub
Complete the level defeating 20 Ewoks or more
You will probably get this without trying, but you have to kill at least 20 Ewoks in Endor.
This is pretty easy, there are way more than 20 ewoks in the level.
Focus on hitting them with A+X to also get the other achievement:
Solution for Sith Kicker In Star Wars: The Force Unleashed IIAs stated by Gdinut, the achievement pops up only when you complete the level, after beating the final boss.