Star Wars: The Force Unleashed

This force power can be used by holding LT and then pressing X. Can be done with Vader against the endless wookies in the first mission. Just stand on the bridge and keep cutting them down until you get



and then this achievement.

Edit: Per the comments a few people have noted that the wookies do eventually stop spawning for some people. I didn't experience that myself, but in case you are one of those probably the best alternative is the beginning of the first level killing storm troopers. Next best would be the TIE Fighter area, but since that isn't infinite respawn, I would just save game and go back to the wookie bridge myself and keep killing there.

Quickest way I found to work on this was to play on the first level (TIE factory) and just keep redoing the first area with the storm troopers and the rebel guys. If you walk down to the end of the first walkway, after force pushing open the doors, there is a sith holocron which will give you unlimited energy so run amuck and spam saber throw as much as possible. When the middle opens up and groups of eight stormtroopers show up you can often get multiple kills with one toss. Also jump as much as possible to avoid deflecting laser bolts back onto would be saber toss targets. After the room is cleared out pause the game, hit save game and then either go into mission select, select TIE factory and load last save point or change your costume which will put you back at the beginning of the level but remember to hit SAVE GAME or your kills won't be carried forward. Rinse and repeat. Yes this will be tedious but probably the easiest way to go about doing it.

In my opinion it's very boring to sit there and just keep throwing your lightsaber 500+ times. This video: is a way to do this achievement MUCH faster, and with much more variety and skill. Note: If the wookies stop spawning. No worries. All the kills that you have accumulated will still count when you load the game again. Just make sure to:
-Save Game
-Exit Game
-Continue Game

Step 1 - You guessed it, start a new game on apprentice difficulty (or use a game already in the very beginning, in the level where your Darth Vader.)

Step 2 - Yup, get to the bridge where there are unlimited wookies.

Step 3 - .....FINALLY something new, I know, I know. Stand in the hut that connects the two bridges together. Make sure you stand in the very middle of the bridge that the wookies run across, BUT not actually on the bridge
(just before it) (Video makes this more clear) (About the video, sorry about the angle)

Step 4 - Use RT (Force grip) to grip any wookie. DO NOT THROW HIM!

Step 5 - Move that helpless wookie onto the bridge (Touching it) as far as you can make him go (towards the opposite end of the bridge)

Step 6 - Now here's the more skillful bit. YOU HAVE A GODLY AMOUNT OF HEALTH, AND KILLING ONE WOOKIE WILL FILL YOUR BAR TO FULL, DON'T WORRY ABOUT YOU GETTING HIT! DO NOT PANIC WHEN GETTING HIT! (And yes you will get hit). move the wookie that you're holding to the side of the bridge and wait until some wookies pass (unless they're all next to you, in which case just throw your lightsaber until most of them are dead). When they pass they should be in a straight line. (Or close to one). When they pass move the wookie your holding directly in line with them.

Step 7 - Throw your lightsaber (X while holding RT). Note: When your lightsaber hits the wookie he will die, but you will still be holding his body, so there's no point in getting another one.

Step 8 - Repeat step 7 until achievement achieved. (Repeating 5 and 6 is optional) Note: You will eventually run out of force, and you will have to wait until it recharges, but you can use this time to slash the wookies around you to gain health)

What this should do, is hit multiple wookies; (killing them). This saves an immense amount of time, because you don't have to throw your lightsaber as much. You should hit 2-5 of them in just one throw.

In all likelihood, you got this game to play through it, and if you're like me, you glanced at the achievement list, saw lots of "kill tons of enemies," and you thought to yourself: "No problem, I'm playing through the entire game. I'll pick it up as I go along."

Now, you're sitting there, like me, wondering where to go with this after completing that story mode since you cannot replay the prologue AND your kills won't carry over to your Sith Master save, nor can you carry them over to that Jedi Temple DLC. That means all of the wonderful solutions you've been reading won't work at all if you want to keep all of your progress. Are the Jedi Temple and Prologue good places for this? Sure, if you haven't started or want to start over.

My personal grinding point for this and all the other "kill with skill" achievements was (as noted by airjedi in another solution here) the Tie Fighter Factory, right at the beginning at the level. You spawn in a hallway with some droids (wipe them out if you haven't grabbed the kill 35 droids achievement; oh yeah, and the droids of my enemies are my enemies so they totally count as kills too), and once you get to the end of this hall, you bust the door open with Force Push, and you're in a room with some rebels and some Stormtroopers. At the far end of the walkway where you enter is an unlimited force powerup.

Saber Throw is where you make sure an enemy is highlighted, hold LT, and press X to toss your saber at them. This is the most annoying one, in my opinion, cause as soon as you get a lock and toss, you end up hitting the crate next to them. Trouble with laser bolts deflecting? Reset the yellow talent spheres in Force Upgrades under the pause menu and build them all back up except Defense Mastery to lower your ability to deflect the bolts.

Clear the room which is about 40 or so enemies (nearly 50 if you grab the six droids in the hallway as well). Pause the game. Save it. Select Mission Select, then Tie Fighter Factory, and then Load Previous Save. You'll start at the beginning of that droid hallway. Do it again and again and again until you get the achievement, then pick your next skill, and do it again.

How long will it take? Depends on how many you did during the story since this method at least respects that you probably have some kills on it. Happy grinding.