Other than Aloy and Elisabet, Nil is probably my favorite character in the whole game. He's hilarious and brutal, and he's seemingly got the skills to back that brutality up. He's a little cracked, a bit nuts, but he doesn't direct the destructive parts of that apparent insanity at everyone and everything, he's got his own morals. That he isolates Bandits as "okay to kill" means that other people aren't okay to kill, even if that distinction is purely done out of pragmatism, out of not wanting to get an army on his ass.
I dunno, I just really love this dude, and the choice he offers you at the end of his quest-chain can be heartbreaking and hilarious depending on what you choose. When he was fighting alongside me during the final battle, I hoped he found some peace in fighting for something bigger than himself, to save a world; finally all those combat skills and that brutality could be applied for a grander purpose.
I also like Nil because in some ways he's a stand-in for a lot of game-players. I won't lie, I love making Stealth Kill videos because it's fun as hell. I love killing enemies in games in flashy ways, I love to test myself like that, and there's nothing wrong with it because the game-state and its narrative tells me it's "okay" to do it. I saw a bit of myself in Nil, when it comes to that. (Of course I also love Pacifist play and Ghosting, maybe even moreso, but that's another conversation.)
So yeah, post about your favorite Nil moments, things you noticed about him, and stuff that made an impression on you.
We definitely know that he's Carja, and he used to be a soldier, and a fine one at that. Nil is apparently not his real name.