To unlock this achievement, you need to retrieve the Hot Air Balloon, complete the Puppet Show and Fix the Pirate ship.
Hot Air Balloon: Fix the Carousel, then use the shadows of the ride to climb up. After reaching the beacon on the top of the Carousel, use the new space shaped shadows to reach the rooftops. Don't forget to collect the The Cyclops' bottle for another achievement before freeing the balloon.
Puppet Show: Collect the Princess' hat first then shift into the shadows for the start of the show. The First part includes jumping on 4 Crocodile's heads to cross a river. Complete this on your first attempt to get another achievement. When you reach the Ogre, stand on the stump and dodge the attack to get him stuck then go behind him. He will turn around and try to attack you again. Dodge this and the tree will fall on him.
The second part takes you to a Spider's lair in which you will have to break Spider's web by jumping in to them. There is also a fairly easy chase sequence which ends with you crushing the spider with a boulder.
The final part takes you to a Dragon's lair in which you must taunt the dragon to attack then hide behind the rock located nearby 3 times to burn the ropes hanging Fred. After that you will complete the Show.
Pirate Ship: Take the box and use the light on the right to make a shadow to climb the wall and press the button for Didi to cross. Then take the box and put in on the red gear switch which will activate one part of the door to continue. Next take the box nearby and go behind and shift with the box to enter the Wheel room. Place the box on the blue switch then interact with the wheel and turn it a couple of times. Shift back to the main room and use the shadows of the wheel to get up high and climb the ledge. There will be another box there which you can take and using the wheel get to the green and final switch. Go through the door and ride in the cart with Didi.
When the Cart stops again, make sure to jump in the Treasure chest to get another achievement. Then jump up to the cannon ball carried by the crane and use the button to send the ball to attack the Kraken. When it gets shot out, use the tentacles shadow to get to the ball and shift with the shadows to cross the gap. then place the ball in the shadow world under the shadow crane and interact with the button again to clear the path for you to continue.
For the Finishing blow, take the ball from below and use the right side to get up to the light in the middle. Then adjust the light so you can place the ball on the shadow side near the cannon before returning to the light and adjusting it to actually reach the cannon. You will have to enter the door below, then at the end of the hallway, when Didi says "GO," interact with the switch to restore the generator.
The achievement should unlock when the cut scene finishes and you need to go back to the Circus Tent.