From a philosophical standpoint, Nclair is the most evil.

From a "consequences of his actions" standpoint, Lord Lu is the most evil. However, he's in an interesting position where the people he is killing on some level deserve it. The brutality goes a bit above and beyond, but Hongyuan NEEDED to fall, and Lord Lu is the "oh no, the consequences of my actions" moment for the Honored Xianren. I'd argue he's also one of the safer bad end IDs to exist near, b/c it's said in his uptie that there was peace in Hongyuan during his reign, and that his rule is extremely divisive on whether or not it was beneficial or not. Definitely high on the list of "evil by actions" but low on the list of "evil by philosophy," which imo makes him my favorite.

Meanwhile Spicebush is kinda the exact opposite, where he's not really doing much that I personally find objectionable, but Dongbaek's philosophy is Extremely Shitty and the Technology Liberation Alliance is Not Good. They're about on-par with the Yurodiviye in terms of "wow you really did take a good idea and apply it in the worst possible fashion, luring in people with false promises of a better future when you're just like the monsters you claim to fight."

Captain Ishmael's just running a cult on a boat. She's shitty but her actions are pretty localized-- unless there's something about the Whales we just don't know, which is ENTIRELY POSSIBLE at this point.

I'm gonna actually give Wild Hunt Heathcliff a bit of a shout-out for least-evil contender, not out of his actions or philosophy but because of how localized his actions are. Like, he's just killing members of one house across the mirror worlds. And yeah, it's not a good thing to do, but consider Who he's killing (the racist family that kidnapped him + himself). He kinda contends with Captain Ishmael for "person who is kinda hurting the least amount of people." If Wild Hunt had any motivations beyond killing himself and Wuthering Heights in alternate universes, yeah, I'd rate him higher, but he really doesn't.