Part 2 is also solid, and if anything, I'd have preferred Part 2 to be a template for the movie as a whole. I'm going to summarize a lot of information that isn't presented in this order, but it's easier to set the scene in-universe rather than based on plot.
One year has passed since the RDA has returned to Pandora. In that time, they've established a giant city called Bridgehead, building "more in the last year than we did in the last thirty" (as in, the thirty years prior to the events of the first film). While the RDA of the first film was just here to mine unobtanium, this is full-blown colonization (remember that, because the 'mission statement' gets iffy later), with the intent of turning Pandora into a new home for humanity after the natives are "pacified." I might as well say it here, if you're looking for moral ambiguity here, you won't find it. Apart from a single RDA scientist, every RDA-aligned human is an asshole here. I've always maintained (and still do) that the characters in the first film had shades of grey, but Way of Water has no such thing. Na'vi are good, humans are bad. Which, to be clear, I don't think is inherently a bad thing - plenty of alien invasion movies don't bother with grey morals for the invading aliens - but it does make WOW a very black and white story.
Anyway, humans have Bridgehead, but the planet is fighting back. Jake and the Omaticaya have retreated to the Hallelujah Mountains, and have been conducting guerilla warfare against the RDA, which we see at the start of part 2 in one of their convoy raids - destroying RDA gear, retrieving RDA weapons (apparently the na'vi are fine using guns now, though Neytiri sticks with her bow the entire film). I might as well say that the RDA is hilariously incompetent through the movie in a sense - apart from one major character death, I don't think they kill a single na'vi anywhere, their gunships' cockpits can still be penetrated by arrows, and while the Skel suits are cool (think power armour exoskeletons), they're still useless. On another mention, it's noted that pretty much the entire planet's biosphere is fighting against the RDA. That everytime they enter the mountains, they have 10 minutes before the native flora starts attacking them. It's never really stated outright, but it's pretty much established that Eywa herself is fully aware of the threat the humans pose, and is willing to direct her creatures to fight them. Or, more specifically, humans are triggering the planet's "immune response." How you feel about this is up to you, but me, personally, I think it works - it builds on Eywa's 'character development' (so to speak) from the last film, and really helps solidify Pandora as an alien world with its own rules. Like Earth in many respects, but it's a planet operating as a giant super-organism.
To deal with this, the RDA deploys recombinants - basically avatars implanted with the memories of ex-RDA soldiers, including Quaritch, who's assigned to lead the first (and only?) recom squad. In a nice act of parallels, Quaritch's awakening period is like an inversion of Jake's motions in the first film - wakes up in his recom body, but reacts with terror rather than happiness. Lands on Pandora via shuttle, but takes his mask off rather than put it on. Drifts in zero-g, but his movements are less serene, and so on. Subtle touches, but they work. As to whether Quaritch himself works in the film? I'd say "mostly." There's a dichotomy between old!Quaritch and new!Quaritch, and he alternates (as if unable to decide) whether he should consider himself the same man, or a different man who happens to have another person's memories. It's not something that hasn't been done plenty of times in sci-fi, but in this sense, it kinda works. Anyway, the recoms are sent into the mountains on the bet that because of their biology, Eywa's creatures will see them as na'vi, so they can find out where the rebels (sorry, resistance) are hiding out. It's also at this point that I started getting Star Wars vibes. Make of that what you will.
The recoms are inserted, and it turns out that the wildlife does indeed see them as na'vi. They end up treading over old ground (literally) as they reach the site of Jake's final battle with Quaritch in the first film. In a case of fan service that actually serves the plot, we see flashbacks to the fight as seen through the AMP suit's onboard camera, as recom!Quaritch gets to see his old self die, recovering his old self's dog tags, and crushing human!Quaritch's skull. Nothing groundbreaking, but nice stuff. Turns out, however, that the kids have also stumbled into the area and are taken captive, while Jake, Neytiri, and Neteyam move into attack them in something that's part-Vietnam War, part-Predator, under the cover of an eclipse (eclipses happen three times in this film - apparently its fairly common, as Polythemus passes between Pandora and its primary star). What follows is a gun/bow fight under darkness and in the rain, in what's a pretty neat action sequence. Quaritch wants revenge on Jake, Jake and Neytiri are understandably spooked by Quaritch being, y'know, alive, and so on. I've seen a lot of people praising the film's final action scene, and while I agree with those sentiments, I honestly think this might be the best action scene overall. It's tense, it's moody, it's well shot, etc.
Up to this point, I'd call the movie solidly "good." 8/10, 7/10 at the very least. However, it's after this sequence that the movie takes a sharp turn into the deep end. I honestly thought a scene must have been missing, but Jake, spooked by Quaritch, reasons that he and his family have to flee the mountains as Quaritch will never stop hunting them, that because of Spider, the RDA will soon learn the ins and outs of the area. Okay, first point - the RDA was already hunting you before this, Quaritch returning, while spooky, doesn't actually change much. Second, that Spider has been captured puts everyone at risk, not just Jake and his family. If anything, it makes Jake look like a selfish asshole, because he's running with his family, leaving the Omatikaya to continue fighting, despite the fact that they're now more at risk, and by Jake leaving, they've lost their best asset (since as an ex-marine, he knows how to use guerilla tactics, use human weapons, etc.) This is arguably somewhat mitigated by the fact that WOW doesn't really have a single main character (if there is one, I'd argue it's Lo'ak), so Jake being an idiot/coward doesn't derail the plot as much as it would otherwise, but this move is just bizzare to me. It's like Cameron needed an excuse for the Sullys to go island hopping, and didn't think ot out.
