Nere is probably the best example of how lacking and generally railroady the evil routes of this game are. He has unique loot that yu can't get if you let him live. He dies anyways if you spare him, despite his offer to recruit the Order of Soul Spiders as allies (seems like obvious cut content for the endgame where you gather all your allies for the final battle), doesn't reward you with anything meaningful if you save him, and is written in such a way to make you despise him, even if you are rp as an evil character.
And to boot, his death is required for the resolution/continuation of several plotlines. The whole thing with the Deep gnomes and Barcus, and his head for the Myconid questline.
You get nothing of worth for helping him and lose on a ton of things in tradeoff. Nothing in his interactions has any followup later in the game despite indicating it will. It's a huge letdown, honestly.
Honestly, I kinda like him better than Minthara in some respects. Despite her great acting, I'm kinda disappointed with how Larian wrote her to be nicer and more accepting despite being an evil-run exclusive party member. Nere is at least consistently a reprehensible person, and he's faithful to Lolth, which would be a nice break from the 'ubiquitous heretic drow party member' that D&D rpgs love so much.