I'm leaning more toward a Dark!Spider. Dark meaning: He's not evil, not misguided, and certainly not living up to everyone’s negative expectations just because he’s the son of a war criminal. This version of Spider is abrasive, sharp, calculating, merciless, and utterly unforgiving. The way the adults around him treated him taught him early on to rely on no one but himself. He grew up bitter and cynical, far too mature for his age, self-trained, self-taught, and sustained only by Eywa and the wilds of Pandora. He's even prepared in secret for the inevitable day Neytiri or Jake might decide to "get rid" of him to appease Quaritch’s victims. When that time comes, he’ll be ready.
This Spider is a mouthy little shit with a blade as sharp as his tongue, cutting others down with cruel, pointed words, a talent he picked up from Neytiri herself. Her past insults from his childhood were his first lessons in pain. He's learned from her coldness and backs up every word with skill. Fast, vicious, and precise, he knows how to leave deep cuts. Both literal and emotional. He moves like the Crannogmen from Game of Thrones, with total mastery of Pandora’s brutal terrain. He’s not evil. Just a hurt, traumatized kid using pain as armor.
Spider even calls himself the Forest Demon or just The Demon, wearing the insult like a crown, a warning, a defense. If that’s what they see, then that’s what he’ll be. And he lives up to it by terrorizing RDA soldiers without hesitation, without mercy, without guilt. Spider is everything the adults built him up to be and more. They will simply have to put up with it.