Dude, no one is saying she has to be a disheveled wreck. Most people are just saying that she comes across as very boring and lackluster. There is so little emotion or intensity to her. If her thing is "I finally made it back, thank god!" Then that's fine... sell it. Sell the shit out of it. Have lines about how she missed grass or wind or trees. Have her sound determined not to let the void spawn ruin this world like they did their own.
Give her some freaking intensity and emotion. I've heard people say she's supposed to be emotionally muted because she had to kill off her emotions to survive... or that the symbiote deadened them. If so, they undersold that too. She doesn't seem unemotional... she just seems bland. And if her thing is supposed to be relief on being out of the hellscape (even if she's handled it well and isn't crazy... that's perfectly fine) then sell that. She doesn't have any lines that drive home either of those interpretations of her. She just has some basic "back, monster" stuff and some where she bluntly states how she feels or what her purpose is... but in a way that doesn't really sound like she's packing much drive. She's make a terrible inspirational speaker.
She DOES have a line about "I know I'm frightening, but I'm here to help.". And this makes me feel that her hotgirlness was a decision not always intended for her. She does NOT look frightening at all... she looks like a hot girl in a tight catsuit with some goofy wings. Was she supposed to be more alien or monstrous and that was changed along the way? I doubt riot would tell us if that was the case.
I think the problem people have with her is the problem of underselling. Her background is BIG. It implied huge, life-changing crap happened to her. Her ordeal seems like it should have been a powerful thing that influenced everything about her... and that doesn't come across in her design or her VO. Whether she's traumatized, devolved into a monster, emotionally dead, filled with intense willpower and survival instinct or just quietly joyous to be alive none of it conveys well with the performance we got from her. I'm sure her lore story will make some excuses and explain why she is how she is, but it won't make her feel any more interesting, I fear.
Riot has done well with this in the past. They sold the hell out of Sion's berzerker status with occasional lines that he realizes he's become something horrible and he can't escape it. Poppy is a plucky, humble hero and that comes across well. Warwick is a monster trying to remember his humanity through a haze of bloodlust. Swain is a stoic "ends justify the means" sort that will sacrifice anything he needs to if it will further his goals... which he sees as commendable. Riot is usually pretty decent at this.
But Kai doesn't have that kind of performance or passion in her. She doesn't really feel like a character... more like a shadow of one. She doesn't even feel like a character that they meant to to be a shadow of herself after her ordeal. She just seems like she's got no soul to her.
. I didn't read a lack of emotion like everyone else did, I read a release of tension. Not everyone coming back from trauma is irrevocably damaged, sometimes it gives you perspective, even if it is extreme. Kai'Sa genuinely sounds like the most well-rounded human being in League even if her personality isn't particularly adventurous.
