Unlike the usual situation with the Hubs coming out of the last level places you into the start of this level, and all that you need to do is pick up the block in front of you and throw it through the target on the wall ahead...
After the opening CS in which we see just how deeply Unikitty cares about Emmet -- and just how powerful she actually is -- The Overlord, Lord Business makes an appearance!
Before we can deal with LB we have to take out the Micros and troops, after which we begin a game of attrition in which Unikitty uses her fire beam to take out the panels first on one side of the Spider's Head, and then the other, with Emmet tossing nice heavy objects into the broken sides with each success.
Once you complete the path to the final rooftop the now wounded LB will attack with the two front legs of his Mech Spider.
Every third attack or so a leg will get stuck, at which point you attack! When you break a leg off, pick it up and throw it through the cracked side of the Spider. Rinse and repeat and then pull the Spider down and smash it, destroying the Mech and triggering the final CS of the story mode, in which victory, as they say, is yours!
-- Post Level Stuff --
You get the Level Unlock notice and the FreePlay Unlock Notice, followed by unlocking the Achievements "You Can Still Change Everything" (20G) Completed Level 15 - The Final Showdown. You also unlock "Including, But Not Limited To" (20G) Purchased All Master Builders.
In addition to the above, you obtain the FREE Character Gandalf, and you unlock the characters Vitruvius (Ghost), Gordon Zola, President Business, and Lord Business (Minifigure).
Hitting "Continue" now plays the credits, and then places you in The Bonus Room - which is a special area in which the Golden Page Kits can be build when you have the completed sets.
You can now purchase the remaining characters that you just unlocked for a total of 2,760,000 Studs, which will then unlock the Achievement "The Special People In Your Life" (40G) Purchase All Characters.