General Grievous: Duel of the Droids
Brace yourself, because General Grievous's story is the most grueling, but it's mostly grinding activities rather than anything else. So let's get started...
Walk up until you see the electrified wall, and use RS-S6 to activate the nearby panel. Let Captain Rex activate the newly appeared panel, then destroy the rubble to the right of the hole in the middle. Use the Force to build a hook from these pieces, and let Captain Rex grapple it, then activate yet another new panel that appears.
Now you can head forward to the next dead end. Cut a hole in the electrical box to the right of the hole, grab the hook inside, and activate the panel. Have RS-S6 open the door again, kill the enemy robot, use the Force to move the power source to the open outlet, and activate the new panel.
As you move down the hall, stop at the RS-S6 panel and use Rex to grab the hook above the exposed robot. He'll also need to activate the panel that's left behind.
Onto the next dead end... Use the Force to build the hook near the central hole, knock it off with Rex, and attack the killable robots before using Rex to activate the panel that appears.
Go to RS-S6 to open the door, use the Force to defeat the creatures, and use Rex on the panel. Finally things will start to shake up a bit in the next room, after you activate the Rs-S6 panel.
Go down the left door with Rex to get that panel. You'll also need him through the right door. Hitting both panels will trigger a cutscene.
Now it's time for the first of what will be many General Grievous battles.
First up, use the Force to throw objects at him, then attack with your light saber. When he has one heart left, he'll dash away. At this point, build the golden droid in the middle of the room; it'll destroy the golden block to your right, revealing a jedi symbol.
Use that, then climb the stairs to your right. Hit him with your saber, then use the Force to place the bomb on the purple piece nearby.
Time to switch to another screen. From here, rush down to the end of the hall and use the jedi symbol to cut through. At the end of this hall, assemble the Lego pieces to the left and use the panel to disable the force field.
Now you can use the Force to create your good friend, R2-D2. Use him right away to activate the panel at the back of the room. Walk down the hallways that opened up - stick with R2-D2 to get the panel on the right side.
Use R2's hovering ability to cross the gap and activate the next panel. Get the enemy droid and the next panel and then switch to Anakin. Go to the center of the floor and use the Force to build a torpedo generator.
Now head to the right and open the big container with the Force. The pieces will allow you to assemble a speeder jet. Jump into it, fly over the torpedoes, and nab the purple target.
Now go to R2-D2, knock out the droid that appears, and activate the nearby panel. Back into the speeder you go, and hit the torpedo targets. Boom!