From Blake Snyder's book, SAVE THE CAT, here's what he advises for the finale:
"This is where we wrap it up. It's where the lessons learned are applied. It's where the character tics are mastered. It's where A story and B story end in triumph for our hero. It's the turning over of the old world and a creation of a new world order -- all thanks to the hero, who leads the way based on what he experienced in the upside-down, antithetical world of Act Two."
"The finale entails the dispatching of all the bad guys, in ascending order. Lieutenants and henchman die first, then the boss. The chief source of the "the problem" -- a person or thing -- must be dispatched completely for the new world order to exist. ... the finale is where a new society is born. It's not enough for the hero to triumph, he must change the world. The finale is where it happens. and it must be done in an emotionally satisfying way" (page 90).
For more information about Blake Snyder's method: