system
Given the following post, respond as if you're commenting on Reddit:
human
[Avatar 2] Left with no choice the humans return home and amass a more powerful force to return to Pandora. They move away from the slow tactics that lead to there defeat. What weapons and tactics do they bring back to defeat the Navi.
gpt
Tactical orbital bombardment of major Navi settlements and drone strikes. There is absolutely no need to go toe to toe with the Navi, and in fact it's quite dangerous to do so. Nuclear weaponry would be unlikely for several reasons. One is that it would make unobtanium harder to mine if the landscape were irradiated. Two is that large numbers of nuclear strikes could have disastrous effects on the planets weather patterns. Remember, there are a LOT of Navi, and nuking all of them would be send the planet into a nuclear holocaust.

Conventional bombing would do the trick. The Navi live in trees for the most part, and don't have much of a defense against standard bombing. They're not about to run into a cave system to take shelter, at least not at first. On top of that they have no defenses against bombs whatsoever. None. They can't shoot the bombs out of the sky with ordinance of their own. If bombs are being dropped from high enough they won't even have the capacity to reach the bombers themselves (as everything they fly on can only do so whilst there's an atmosphere for them to do so).

Drones would be ideal at mopping up survivors. They'd move faster than any of the Navi rides and would have a shitload more firepower. On top of that they can fire from miles away with exceptional accuracy. The Navi wouldn't stand a chance.

The real issue would be that eventually the humans are going to want to mine for unobtanium. If they don't eradicate *all* the Navi (and they won't be able to as it's a big planet) then there's a high likelihood of reprisal from the survivors. This is where the real issue comes into play for the humans. Fortifying the mines would be difficult and costly, which means they're going to want to limit the number of mines that they have.

In all likelihood, the humans would bomb the crap out of the large unobtanium deposit, which is the big soul tree thing, to kill vast numbers of Navi there, and then land and start mining it. They could spend a lot of resources on fortifying that area while still maintaining a cost effective project. Any Navi that come close would be subjected to bombardment and drone strikes.

After destroying the cultural center of the Navi, the humans would attempt to subjugate the remaining survivors. After a few generations in the Navi would have lost a lot of their will to fight, and lost a lot of their old culture. Broken Navi would be used as labour in new mines. Humans would attempt to get Navi hooked on something that only the humans could provide. Drugs, booze, something like that.

Essentially it would be cultural genocide through the initial use of overwhelming force, and then through cultural trappings and re-education. Humans would sell the whole thing as trying to make the Navi civilised.