OK, so, for the first 3/4 the film sticks pretty close to the book, not much I can say about it from there. BUT THEN.
The fight scene.
Oh my fucking god, the fight scene.
For those who haven't read Breaking Dawn, the gist of it is that some bitter vampire reports the Cullens to the Volturi (Twilight vampire government) because Edward and Bella made a vampire baby, and that's frowned upon. It all comes to a head with a face-off between the Cullens & their friends against the Volturi, and it looks like there's going to be an epic battle, before they all just talk it out, and go home to sparkle another day. Lame anticlimax is lame, etcetera etcetera.
This is what everyone was expecting when they went to see the film.
That did not happen. What transpired instead was possibly one of the most glorious moments of cinema history:
The stage is set. The Volturi are gathered on one side, the Cullens & Co. on the other. Everything is going according the plan. The Volturi are about to destroy the Cullens, but then Alice Cullen (who ran away mysteriously earlier in the film) comes back just in the nick of time with just the plot device to prove that her and her family are innocent. And then ... it fails. The film!Volturi instead decide that unlike their literary counterparts, they aren't having any of it, and heads start flying.
Carlisle is burnt alive, Jasper's head comes off, and then a whole bunch of werewolves (incl. Seth and Leah, I think) get offed. Hell, at one point I thought Bella's head was gonna come off, or even Renesmee's. And it scared me. None of us could believe it, everyone was going crazy. Women were sobbing, boyfriends were cheering, it was beautiful.
But then the Big Bad's started getting offed, and it became a whole new level of awesome. The haters in the audience like myself had seen these holier-than-thou Sparklepire snowflakes get smited for once, and smited so hard that we started cheering for them, or at least enjoying their victories. My personal favourite bit (God, I never thought I'd say that about a Twilight film) was where Alice, the one likeable character of the entire series prior, ripped Dakota Fanning's head clean off. One of the good vampires even ripped a bad guy's head off by the roof of his mouth. It was amazing. I even enjoyed the bit where Bella & Edward teamed up to kill Aro. Dear lord, I was rooting for Bella.
Sadly, however, the crew could only deviate so much away from the source material, as they had apparently been given strict instructions to stick to the source. So it soon turned out it was all an elaborate hoax. Yes, none of it happened, it was just a vision Alice had had of the future (since that's her vampire superpower) that she had showed the bad guys when she had arrived with her plot device earlier, to show them what would happen if they didn't back off.
This was even even better, actually, purely for the audience reaction: the boyfriends were sort of pissed (I remember vividly one of them shouting "this blows!"), but the women? They were at a loss for words. Some of them seemed relieved, but others were ... sad? I think ultimately the fight scene was a wake-up call for some of them. They saw how epic the Twilight SERIES (it's not a saga) could have been, and were then subjected to the harsh reality of the bullshit they'd been buying into. It was a very soulful moment, in retrospect. At least, for some of them, anyway.
Of course, other things did happen in this film, but everything that happened beforehand simply pales in comparison to those ten minutes of concentrated win. That scene just made the film. If everything had gone according to plan, BD: Pt. 2 would just have been remembered as the particularly rancid end to an abysmal series (well, the film series, anyway). So kudos to you, cast and crew of BD: Pt. 2, for having the balls to challenge your audience. I salute you.