The final instalment in a film franchise often comes to define the franchise as a whole. The Return of the King cementedPeter Jackson's reputation as an extraordinary fantasy filmmaker who moved the goalposts for both cinematic technology and fantasy storytelling. Evil Dead 3: Army of Darkness and Spider-Man 3 both saw the wheels come off, with Sam Raimi throwing everything he had at the screen to disguise the fact that he had run out of ideas.

With Harry Potter and the Deathly Hallows - Part 2, we already had a fair idea of where we were heading, if not by the end of Part 1, then by the ending of Half-Blood Prince. Coming in somewhere between the dizzying heights of Alfonso Cuarón and Mike Newell and the disappointing lows of Chris Columbus, David Yates' instalments have had a lot going for them on a thematic or tonal level, but have also been hobbled by too much plot and a lack of weight in some of the main developments. Considering where the series began, the film is a triumph; considering where it could have ended up, the joy is much more muted.

Much like The Return of the King, much of Deathly Hallows - Part 2 is concerned with the characters' relationship with death. Even moreso than in the previous instalment, the characters find themselves in an endgame, where they are fighting against a seemingly inevitable outcome. Voldemort has never been as chillingly scary as Sauron, but in this film his desperation and panic over dying makes him more threatening. There are still times when Ralph Fiennes over-eggs it, but a lot of Voldemort's childlike fears of death and mortality are finally brought to the fore.

How precisely the film deals with death is quite a conflicted matter. As in the previous instalment, there is the seeming need for a lot of characters to be killed off simply as a means of ending their character arcs. Bellatrix Lestrange's demise is dealt with far too quickly to be satisfying, while more lovable characters like Remus Lupin and Nymphadora Tonks don't get the screen time they deserve to make the appearance of their dead bodies carry meaning. Having invested so much in many of these characters, dispatching them so fleetingly - even in a war - is a bit of a kick in the teeth.

To put it bluntly, Deathly Hallows - Part 2 attempts to strike the same kind of balance that Jackson sought in The Return of the King, but is only partially successful in doing so. On the one hand, it acknowledges the need to show the scale of the war and the extent of the atrocities taking place; it's happy, in other words, to give us the Potter equivalent of the Battle of the Pellanor Fields. On the other hand, it seeks to be reflective and introspective, bringing the conflict down to the level of Harry's conscience and his final connection to Voldemort.

Given Yates' dodgy track record with action set pieces, it's no surprise that the Battle of Hogwarts' treatment of death is the weaker of the two approaches. The special effects are all fine - you won't find the same wretched over-abundance of CGI that you'd find in the Star Wars prequels. But while Jackson's battles had pacing and structure, with clearly defined yet unpredictable movements, the Battle for Hogwarts moves in fits and starts and isn't all that memorable. Yates tries to include as many of the little moments from the books as he can, but he struggles to link them all together. If the Battle of the Pellanor Fields is like a Wagner opera - big, bold, brash and often breathtaking - this is more like a high school violin recital: still impressive in places, but timid by comparison.

In its more candidly introspective moments, however, the film takes flight and we find ourselves bonding with Harry a lot more than we would if he was solely in the heat of battle. Both the dream sequence in Kings Cross Station and the all-too brief sequence with the Resurrection Stone give the film the space it needs to breathe, reminding us of the emotional baggage which Harry carries and why he is fighting in the first place. It's to the credit of Yates and his colleagues that such scenes are allowed to take up so much time, when in a standalone or franchise-launching blockbuster, they would be lying on the cutting room floor.

The visual bleakness which Yates strove for in Part 1 is reinforced strongly here. The entire Kings Cross Station sequence borrows heavily from 2001: A Space Odyssey, using white light in a way that is intrusive but also comforting in the context of the action that surrounds it. The whole colour palette is more washed out, with the blues and blacks of the Hogwarts uniforms appearing dusty and battered even before the battle has started. This at least gives a semblance of tonal consistency, linking the battles and quiet moments together quite well.

The other big highlight of the film is the revelations regarding Snape. This is one aspect of the series in which what might be called 'the long tease' has worked: we have been held in suspense successfully for seven films, still unsure as to who Snape really is or where his loyalties lie. The revelations are powerful and moving in their own right, but Yates plays a clever trick by letting them unfold as memories. By using visual images, such as the flower unfolding in Lily's hand, he avoids it just being another exposition dump, and allows Alan Rickman the space he needs for Snape's death to matter.

Much of the film, of course, is still concerned with the hunt for the horcruxes, which give the first part a sense of structure and progress that it desperately needed. There's a very nice sequence right at the beginning where Hermione has to pretend to be Belatrix in order to enter her vault at Gringotts and take Helga Hufflepuff's cup (a suspected horcrux). Helena Bonham Carter demonstrates her acting chops in this scene, not just playing another version of the character but adopting Emma Watson's mannerisms and vocal tics perfectly. The scene is slightly spoiled by Harry's use of the imperius curse, but we can let that slide.

Unlike the last film, however, the search for the horcruxes seems less essential as Part 2 rolls forward. This is partially deliberate, since the horcruxes in themselves are a plot device rather than an end point, but it's also an admission on the part of the filmmakers that people are only really interested in Harry and Voldemort's confrontation. The progress from one horcrux to another is still entertaining, particularly Harry's self-sacrifice to Voldemort in the woods. But being the last film in the series, we still grow impatient for things to get to the point.

Having finally reached that point, the film has some difficult decisions to make. The final confrontation between Harry and Voldemort has to do a lot of things to pass muster. It has to be visually impressive, giving casual fans who aren't encrossed in the mythology an indication of its significance. It has to capture the different attitudes of the characters towards death, contrasting Voldemort's self-hatred and fear with Harry's more philosophical approach. And it has to last long enough to make it seem like a big deal, but short enough to so that it doesn't drag, as happened with the 'climactic' lightsabre duel in Star Wars: Episode III - Revenge of the Sith.

Given the expectations of both fans of the books and people who have followed the films, it's inevitable that there would be some degree of disappointment. But the final showdown comes up short in all three parts, albeit by not quite enough to completely derail it. It's less visually impressive than the duel at the end of Goblet of Fire, and a little less threatening in places. The subtext is there if you look for it, but Yates is often too absorbed in trying to make wands a threatening weapon to bring it out in the build-up. And while it is better directed than George Lucas' lightsabre battles, it's ultimately too static and straightforward, giving the impression that it goes on longer than it does.

To an extent, the final duel sums up the film, taking characters which we have followed and seen develop, and putting them in situations which are somewhat underwhelming in terms of how they use said characters. Before the oh-so-controversial epilogue - a whole lot of fuss about nothing - we get one last example of this, where Harry decides to destroy the Elder Wand. This is more decisive and logical than the book (in which he simply buries it), but the film misses out on the chance to explore this dilemma in more detail, just as Harry's relationship with power was explored in Half-Blood Prince. We're not expecting moral quanderies along the lines of Genesis of the Daleks or even The Empire Strikes Back, but even a little something would have been nice.

Harry Potter and the Deathly Hallows - Part 2 is a partially successful means to bring the curtain down on one of cinema's most enduring sagas. The cast are generally good as always, and David Yates deserves some credit for having so much introspection in amongst the bombast of battle. It's a flawed beast, like all the Potter films, letting us down in many of the key moments and being lazy when it really can't afford to do so. But as a means to say goodbye to a beloved character, it's not without merit.