At around 2:17 spider is shown running off the bridge down to the deck. While on the bridge and running he is not wearing his mask/breather but has it on when he reaches the deck.
Miles Quarrich got his facial scars before he ever met Jake Sully. But in the recording where he urges his clone to hunt down Jake and kill him, the scars are absent.
High velocity rounds fired from a gun will have very poor penetration through water, in tests done with a 50 caliber armor piercing round, it disintegrated after only about 14 inches of travel through water.
When Lo'ak is being chased by the shark-like creature through the corals, there is a moment, just before he begins to convulse, where the white feathery creatures attached to the coral next to Lo'ak's head seem stiff and plasticky, as if they forgot to animate them. In the next moment, the same creatures are swaying softly in the current as expected.
Spider talks about the moon pool of the antagonist's ship (a moon pool is an opening in the bottom of the hull, giving access to the water below). The Italian version translates this as a meaningless "pool shaped like the moon".
The main characters leave their home village so that the bad guys coming after them will no longer target the village. But the bad guys don't know any of this, and no effort is made to tell them. This defeats the stated purpose of leaving.
Pandora is filled with animals, most of them predators. How did Quaritch's body just lay on the ground for 15 years without ever being disturbed? The smell alone would have drawn animals in.