LEGO STAR WARS: The Force Awakens

The walkthrough writers give a good description on completing the level:

Take out 15 TIE fighters, and then get through the long on-rails section. When you're flying around in a fixed banking maneuver, you need to destroy enough red pipes to get the counter to 100%.
As Finn, just try and stay alive until Kylo Ren takes a big swing at you, at which point you should hit the prompted button and then mash the second prompted button. You'll know if this is about to happen if you lose control of Finn and he moves to square up to Kylo. Do this a couple of times and Kylo will put Finn in a Force hold. Switch to Rey and hobble over the fallen trunk. Multi-build either way to make a gun. Back to Finn, use the same technique as before to land another blow. As Rey just mash the prompted button to grab the lightsaber.

Roles reversed now. As Rey, hold out until the button prompt and then hit Kylo. You won't have to mash a button this time, Rey takes over. When Kylo has stars around his head smack him about until he jumps to safety. Deal with the troopers and then repeat the fight with Kylo. When Rey is force-held, switch to Finn and pull down the middle tree. Have both characters push the big rock all the way to the right. Down in the fiery chasm, just press when prompted to hop across to safety. Then have Rey wall-jump up the narrow chimney at the back. Run at Kylo and simply mash the prompted buttons to finish.

Here is a video walkthrough:
Credit to HappyThumbsGaming.