Just picture a scenario where the group and some allies are trapped in an rda base they thought was empty or in one where the info was wrong and its more heavily guarded. They're cornered in a room, are out of arrows, and they have wounded as they search the find a case with weapons made for the rda avatars and as much as they hate it they know its their last option.

Imagine these four na'vi methodically moving through the halls of an rda base like a well oiled tactical machine clearing out rooms and picking off rda soldiers with such clean precision it'd make Quarich jealous. They cover Teylan as he hacks doors, Ri'nela and Tamtey giving Nor cover fire as he rips open mechs, or Ri'nela using military hand signals to give orders to the others even as the rda fires at them, or imagine Tamtey silently moving through the ducts to flank them before they even realize they're missing or snipe them from higher vantage points.

When they split up it's just as bad, they end up dog piling on mechs, shooting grenade boxes and fuel tanks, silently taking out soldiers with just their hands. Not a single bullet is wasted, they don't fire constantly at one target but fire in short quick burst; they know how many bullets it takes to take out a human and that's all they need.

And the thing is that they hate every second of it. They're being forced to use the very weapons they were forced as children to learn, so any chance of mercy against the rda is out the window, they're whole mentality is "you pushed us to this now you reap the consequences."