I also wouldn't say they were a villain, I'd say they needed help because they're insane. What they did isn't excusable, but that's not the same as them being, at their core, evil.

But of course, as per statement before, all oldwalkers are insane. It's the territory.

You can't say "they need help", and also say "all oldwalkers are necessarily insane." If the second statement is true, then they can't "be" helped, and all that you can do is put them in a padded cell or a pine box before they can harm anyone else. And I think the latter is **** storytelling. First of all, you're prohibiting character development by saying that some aspect of their personalities can never change. Second, if their actions are caused by just being insane rather than being illustrative of some sort of deeper character, then why should we care about their actions?

It's made painfully clear Nahiri isn't insane. She kept her mind stable by thinking of Zendikar, and didn't go on outright irrational behaviour. As an oldwalker she wasn't at all deranged or grandiose.

She murdered thousands both because Sorin was a dick, but also because she legitimately thought Innistrad was a wicked place.

She was aware of her actions. She willingly attempted genocide because Innistrad was a place fitting for a monster such as Sorin.

Dovin Baan at least wanted to prevent death. Nahiri went out of her way to cause it.

Kaladesh will forever go down in history as the block with a white villain not even Helios could hate.

I mean, that's the entire point of the Ice Age story? (and Planeswalker) It holds pretty true considering all the oldwalkers we've seen. I can only think of... maybe 3-4 that were pretty normal, but it's exceptionally hard to judge a being with so much power that is literally older than most civilizations. Even if you call them evil, there's not a lot you can do that matters in the face of what they are. They certainly don't recognize that you have any moral authority of them.

Because of how they affect those around them, not because of how they affect the walkers themselves. I mean, there's a reason all the best characters were just working in the shadows of those titans. Jhoira, Barrin, Jodah, Xantcha, etc. They all had to deal with the fact that the beings around them were more force of nature than human. (okay, so basically all of those boil down to Urza, but Freyalise, Leshrac, and any number of others ran roughshod over mortals too)

And that doesn't sound crazy to you?

In the end, she has a very specific vendetta. I can't see her turning up as a villain outside of that purview.

To me, Nahiri didn't come off as "insane" in a Victorian sense. Instead, she seemed irrational, violent, and unconcerned with anyone except herself. It's possible that this is the result of her having a mental breakdown from the stress of fighting the Eldrazi, or of Emrakul influencing her mind in order to manipulate Nahiri into summoning her to Innistrad, but it could just be bad writing. After all, starting a bloody conflict over something petty because the writers needed an excuse for a conflict was like, exactly what the renegades did in Kaladesh block. It's hard to tell when the author is having a character do something because they want to tell us something about the character, and when the author is having a character do something because we need to progress the plot.

I think that's a fair criticism.

Like Cato said, and also because her mentality didn't change outside of being in pure despair.

It's possible she's not going to repeat this, but her actions are atrocious. Murdering thousands both to spite a single person and because she outright hated them.

I find myself really agreeing with the "he ruined her garden so she smashed his ant farm" mentality. Remember, after Nahiri started watching over Zendikar as the Eldrazi's jailor, she did try to have romances and relationships with mortals but they all kept dying and she eventually became jaded. What's really tragic to me is that Sorin was the one person on Nahiri's level, someone who wouldn't age out and die, someone who understood her, let her down in one of the worst ways possible. I think that's part of why she snapped - he was the last interpersonal connection that she really had. After she got tired of watching mortals die she hibernated because she just couldn't take it anymore. I feel sad for her. And as much as she kept her mind together while in the Helvault, I also think she still cracked more than a little bit. It doesn't surprise me that she ultimately puts little to no value on human life.

I don't think of her as evil though. She's crazy, embittered, and emotionally damaged. She's lashing out and reacting. She doesn't take joy in the suffering of individuals beyond the pain it causes Sorin. She's looking to make him feel like she did.

Her malice was still there as shown by her disgust of Innistrad as whole (in the story when she marched with her cultists).

Still, that is a point of view that could colour her future arcs. I she's no longer able to relate to mortal experience, then she is no longer bound to be restrained or really compassionate.