I remembered this thread a while ago thanks to a post I wrote about The Return of the King...
WARNING: spoilers of The Return of the King.
...and how an important battle ended in a way that can be considered anticlimactic.
Well, the same exact thing happens in Se7en:...
...police thrillers usually end when the good guys face and catch the bad guy (you can think of that as a final battle), and that moment is very important, not only because it's the culmination of a search that has lasted the whole movie, but also because there are usually (and preferably) a lot of things at stake, so if the battle goes wrong, a number of terrible consequences (more murders, generally) would be triggered.
Now imagine that that incredibly relevant battle, the climax of the whole movie, was reduced to something as lame as the murderer just turning himself in to the police with no resistance whatsoever. Well, you've got Se7en: a murderer who is much more intelligent than the cops and who has always been two steps in front of them suddenly decides that he's going to surrender. If Se7en ended here, most people would probably dislike it, or at most, they consider it a good film, but with a terrible ending.
WARNING: spoilers of The Return of the King.
Just for the sake of comparison, apply that to The Return of King and imagine that the movie just ended with the army of the dead killing everyone, and then Frodo just throwing the ring at the Doom Mount without any intervention from Aragorn and the rest, and that's it. That would be a bad ending that people would absolutely dislike (at the very least): no emotion, no tension, no epicity, no nothing.
But as we all know, that's not the case, and after that moment of anticlimax, a bigger climax comes.
And this climax in Se7en basically consists of switching the typical "final battle" of police thrillers for a different one with a much bigger conflict, one internal in which one of the good cops is suddenly forced to face a heartbreaking truth, seeing himself with the strong need of making a particularly tough decision: if he doesn't kill the bad guy, his own wish for revenge remains unfulfilled, and then neither the bad guy achieves his purposes nor he does - both of them lose. But if he kills the bad guy, his wish for revenge gets fulfilled, so he wins in that regard, but at the same time he also loses a lot more: his freedom - and the bad guy, well, just wins.
Now, if we look at this scene in a cold and perfectly reasonable manner, the decision is quite easy: since you're going to lose anyway, it's better to not get your wish for revenge fulfilled, but accept instead a smaller lose for yourself and at the same time don't allow the bad guy to win.
However, what makes this moment so strong is the enormous emotional charge that it has: who in the whole world could actually make a cold and reasonable decision when their so-beloved partner and their just discovered future son, both of them their whole world, have just been mercilessly killed by this utterly despicable son a bitch who is right in front of them right now, while they have a gun in their hands? And that's why the end of Se7en works so well in spite of the previous anticlimax: it brings a much, much stronger climax shortly after, where everything gets solved. And almost inmediately after that climax the movie is over - that, ladies and gentlemen, is how you finish a movie.
So as of now, we have that Se7en not only breaks the paradigmatic structure of the genre it belongs to, but it also uses an anticlimax in the worst possible moment in which an anticlimax could be used, and that alone would already be enough to raise eyebrows if someone told us that such a movie is good. But that's not even all yet.
I think it's more or less common knowledge that villains usually need to have an advantage over the good guys, so that the conflict between them is interesting to follow and the audience feels involved. In the case of Se7en, John Doe (that's his name) belongs to the same group than a couple of widely known villains, and I'm referring to Hannibal Lecter (The Silence of the Lambs) and the Joker (The Dark Knight Rises). All of them share, loosely speaking, the same profile of villain - one that, when done well, may become very loved in the pop culture: some guy with mental issues who has a very high intelligence. It's, in fact, that intelligence the advantage they have against the good guys: they all outsmart their counterparts,...
WARNING: BIG SPOILERS of The Silence of the Lambs and The Dark Knight (and Se7en).
...even to the extent that, one way or another, they all win in their respective movies.
In The Silence of the Lambs,...
...Hannibal Lecter manages to escape and wander freely in some country, where he once even got to have an old friend for dinner.
In The Dark Knight,...
...The Joker forces Batman to sacrifice his image and become sort of an outlaw. (No wonder why he's always so serious.)
In Se7en, John Doe achieves his goal, and I will leave this here for now.
So, as we can see, all of them share several similarities, but at the same time, they all have something that makes them outstanding and memorable. That's why, when you think of The Silence of the Lambs, one of the first things that usually comes to mind is Hannibal Lecter and (more than probably) this image of him. Those crazy eyes totally fixed on you (he doesn't blink, or barely does it, in the entire movie) with that sort of terrifying mask around his mouth, reinforcing the fact that he's a cannibal... The work of characterization both from the creative people in charge of his design and the actor who brought him to life is just excelent.
And if you think of The Dark Knight, one of the first things that usually comes to mind is the Joker and (more than probably) these two aspects of him:
1) His make-up.
2) His laughter.
Just like before, there's an awesome work of characterization behind the Joker that strenghtens his whole personality: the mobs are a joke to him, the police are a joke to him, the whole world is a joke to him... He doesn't believe in anything or have any ambitions: he "just wants to watch the world burn" and laugh at it while it does. And that's what his design and behivior are meant to transmit; in the end, he's just a clown in a circus, isn't he?
And when we come to Se7en, one of the first things that usually comes to mind is... is... is the villain? Let's think about it for a moment - think about... uh, err... what was his name, again? Oh, yeah! John Doe. What a name, eh? Not particularly memorable, I must say, but at least the guy has... uh... ehm... What... exactly does he have? I mean, look at him. He's bald, but not completely bald. He has a hairy chest. He has, uh, a nose. Eyes. Ears. Two of each, to be more precise. Uh... Well, what's more? Oh, yeah: he's a man... who seems to be middle-aged, I'd say, and, uh, who wears an orange suit, but not all the time: sometimes he wears a regular shirt with trousers... Oh, and I almost forget! He can run; not particularly fast or slow, but he can do it.
You get it, right? The villain in Se7en has no characterization at all. I mean, just look at his name: John Doe. John. Fucking. Doe. Can it get more generic and bland? And if we go back to that image of him, what would you think if you see that guy in a random scene without any context? Just based on his appearance, you'd probably have a hard time assuming that he even has a relevant role there, let alone the role of that bright and extraordinarily cruel villain who outsmarts the police all the time.
Now, if we look at the sequence of the car, we can extract a couple of interesting quotes from him:
"It doesn't matter who I am; who I am means absolutely nothing.[...] I'm not special. I've never been exceptional. This is, though, what I'm doing: my work.[...] People will barely be able to comprehend it, but they won't be able to deny it."
"I'm setting the example, and what I've done is gonna be puzzled over, and studied, and followed forever."
So what's precisely what people usually remember when they think of Se7en? Exactly: the murders; his work. John Doe is such a plain and boring-looking character because all that matters is what he does, not who he is; his lack of characterization is his characterization. Or if we stretch it a bit, we could say that his murders are his characterization: you may like them or not, but they're shocking and will inmediately draw your attention, to the extent that you may easily remember them days, weeks, months or even years after watching the movie, just like you remember Hannibal Lecter and the Joker.
But even if the murders are not considered the characterization of the villain, the point is that we could hardly think of anything that would stress the idiosincrasy and motivations of this particular character more than just making him a regular person with no special features at all that would make him memorable, because he's not supposed to be memorable; his murders, on the contrary, are.
And that's why another decision that would spoil any other movie becomes brilliant in this particular one, which makes Se7en almost a manual on how to do things that you're not supposed to do, and yet make them work great and in a way that make total sense (this last point in particular is very important).