If Yotsuyu only flooded Doma castle and did nothing else then no I would not have seen her as something not redeemable. It would have been an act of war against an enemy, at least if it was mostly full with soldiers and not mostly full with civilians. But Yotsuyu has done much worse than that. Show me any of the recent Eorzean or Doman leaders that went to villages and forced friends to kill each other. Show me any of the recent Eorzean leaders that raised their undead soldiers so that they are forced to battle on. Show me where any of the current leaders experiment on people, to create bioweapons. Or where they are hiding a world ending bio weapon like Black rose.
Of course some of that was done in the past but thats the thing. The current city states have overcome that. I will not say a bad thing about future Garlemald if it overcomes what it does and I am sure that there are a lot of good people there too. Does not change the fact that right now its the state who is doing the most messed up things...so much that even someone like Gaius is absolutely disgusted by it. But I guess only dead garlean soldiers count? Not all the massive amount of people that Garlemald has killed, including their own...(Nothing about current or recent Garlemald was about being wiped out...Eorzea, Doma and every other nation they conquered outside of their own homeland had nothing to do with their base conflict...)
And I still dont understand why someone like Zenos is not redeemable and evil (or even someone like Asahi) and Yotsuyu is? Would your view change if they introduce some small sob story for him? Because that is all that was part of her. We found out that some people of Doma were horrible to her including her parents. I might have felt less horrified about her actions if those she killed would have been purely those who personally wronged her. I was even happy when her parents and her brother were killed because they were just as awful. But as we know, she used what happened to her in her past and bascially tormented everyone! Its as if someone was bullied by members of a specific race and then decided to just kill of everyone from that race. How is that redeemable? How would it be morally grey if you and your family die in a horrible way because someone that you dont even know was once awful to your killer? I just dont get that. What if her parents also suffered badly in the past? Would that make up for how they threated her?
Honestly what sense would it make to argue it from her point of view? A messed up person like her would always see it as a right thing to do. After all its totally fine to hurt everyone because specific people were horrible to her. I cant and wont take side with someone like that. Its like saying that you should just view something through the eyes of a genocidial mass murderer or dicator. I wont. I can look at it from the outside just fine and see what awful person they are, no matter what had happened to them in the past.
Also where is that point of view and trying to understand a character when its not the villain or antagonist? Where is that understanding when there is another thread discussion on how the scions should die. Why is it fine to say that one wants Graha or Alisaie dead because they are annoying but as soon as someone does not see eye to eye with someone that is either an antagonist or straight up villain, we are just knee-jerk reacting to it...what does a villian have to do before we are allowed to not like what they are doing, before we are allowed to call him evil or a bad guy?
And where are the examples of this sadistic glee that our character or the scions have? When have we experimented on someone? When have we purely tortured someone? Where is the huge amount of mass death? Or do you really mean the war with Garlemald where it was either to be conquered or to try and take back what was once theirs while hoping that Garlemald does not decide to drop another calamity on them.
I too always grin at the pure sadistic glee of Alphinaud trying to heal garlean soldiers after they tried to kill us. Or the pure glee of Alisaie trying to even save those tempered Garleans. I also cant wait for the sadistic glee that the scions and WOL will show when they free Garlemald of Zenos and Fandaniel and will help rebuilt it.