Many people on here like to try and claim that this character is evil. And well… that is simply not true.
First off it’s been said by Blizzard that she is not evil. It’s simply a matter of interpretation. Both factions in this expansion are at war, and desperate times call for desperate measures.
https://www.invenglobal.com/articles/4755/explore-claim-resources-and-battle-for-your-faction-world-of-warcraft-interview
And also if you read the Horde collector’s edition novella, you will get a little bit of insight as to why the Horde were the aggressors of the current war. Sylvanas is and always has been very cold and calculating. On that note, the Alliance and the Horde are simply nothing more than two groups of people who dislike eachother due to years of conflict on both sides.
But Sylvanas did this bad thing, x, y, and z. Those are not heroic qualities!
You are correct. Sylvanas has absolutely committed very morally ambiguous acts over the years and it could certainly be argued that she lacks heroic qualities.
But if she is not evil but also lacks heroic qualities, what is she? What do you call a protagonist who is lacking in heroic qualities?
https://en.oxforddictionaries.com/definition/anti-hero
Anti Hero.
Anti-heroes are protagonists in a story who lack heroic qualities. They are not perfect Mary Sues but they are not mustache twirling evil either. They often have their own goals and/or methods of getting things done that do not align with their society.
Let’s look at some examples of anti-heroes that we have in this game aside from Sylvanas.
Death Knights – Legion Order hall campaign had them storm Light’s Hope Chapel and slaughter paladins there just so Bolvar could test Darion to see if he’d make a good fourth horseman. Also, in the quests to get their class mount, they asphyxiate a red dragon in order to interrogate it for information about a long dead dragon that the DK later intends to use as a mount.
Illidan – Sacrificed his own mages in order to be able to fight against the burning legion when they were invading Black Rook Hold. Also sought to replicate the powers of the Well Of Eternity in case the Legion were to return again which his people did not agree with and was imprisoned for it.
Forsaken - Scorned by the living due to their state of undeath and have been hunted down and slaughtered by them and as a result have for years worked on a plague that is designed to kill the living and the undead. Their fellow Horde members have been shown to disagree with this action and even forbid usage of it.
Blood Elves - When first introduced as a playable race in TBC, they would suck magic from living beings to sate their magic addiction after the Sunwell was destroyed. A group of Blood Elves known as Blood Knights would steal the powers of the light from a captive Naaru prior to the reignition of the Sunwell due to them losing their faith in the light after the events of the third war. Thrall and Cairne Bloodhoof at the time had opposed these methods.
There are more examples that I didn’t list here because these ones came off the top of my head, but I’m sure you get the idea. Anti-heroes are protagonists who have goals that often times do not align with their society and in some cases, they do show to have some villainous traits. Sylvanas Windrunner as a character fits this criteria perfectly. Her goals and methods have and to this day not sat well with other members of the Horde. But that does not mean she is mustache twirling evil.
TLDR: Evil is not the term you should be using to describe Sylvanas, it is anti-hero.
Also I know the time of me posting this is April Fools, but I can assure you this is not an April Fools joke, thanks for reading! 
