I'm not saying she doesn't have some flaws, but ultimately I think that she absolutely does not deserve the amount of hate she gets. I can see the depth with her character. I can see how beautiful she really is of a character and how tragically peaceful she really is.
Kai'Sa clearly draws a lot of themes from stoicism and eastern philosophies. "While we may not always have control over the things affecting us, we can have control about how we approach things". The stoic seeks self improvement through wisdom, temperance, justice and courage. Letting emotions wash over you and pass as they do, including happiness and joy, anger and pain. Letting them take their course and then letting them go is fundemental in my interpretation of Kai'Sa.
This is really apparent in her voice, in my opinion. Even something like her laugh I can interpret as an expression of these ideas. It draws you in, so full of life. She's lost in the moment.. Full of laughter. Then it fades out, the present is catching up to her. She's back.
Her voice really is a reflection of Kai'Sa taking an approach of clarity and level headiness in life. Kassadin is an excellent father. So many people characterize her voice as boring or un-engaging and I agree at an extremely shallow level it might be, but inspection into her character really shows a depth that resonates with me so warmly. Virtue and self-control is what drives Kai'sa. It is what has allowed her to live all this time.
**It's the void though... How do you expect a nine year old girl not to be radically transformed into something that resembles an actual predator**
This is where I believe her in-game design slightly fails her. The "apex predator" part is a bit too on the nose and isn't reflected well so a lot of people are left with a big question mark with their expectations. However, I could reason that Kai'Sa IS seen like this in the lore. It's evident she is seen and interpreted by Shurimans as an apex predator, a monster, that is evil and whatnot. This could be represented through how she is presented, but is contrasted with her actual personality and stoic attitudes.
**The V-neck though...**
I hate it too, but Riot needs to pay their workers I guess. I have an internal head-canon that the reason she's so physically perfect and clean is that the symbiotic void-spawn wants her to be as healthy of a host as she possibly can be and supplies her body with perfect nutrients she needs to be a pinnacle of health.
Rage, anger, hate. These are all things Kai'sa learnt to deal with. That is why she is so special and why she survived. A feral emotionally driven 9 year old would die quickly. A stable, level headed and strong women survives.