As a Katarina expert and amused of what half the people said.
First her face is younger, the lips are a bit more... her upper lip how more volume and her lower lip is a bit thinner, but at least you got the overall shape correct. The facial structure itself is a bit complicated to draw correct and yours is pretty wrong, she has a bit sharper face and her cheekbones don't really come out that much, even if she's 49 kilos, simply because the shape itself is like that, so skinny fits her perfect. The eyes are a different shape and a bit bigger with a bit of eye lines (not shadows), the eyebrowns are wrong shape and need a tiny bit more volume. The hair is totally horrible, you need to fix that at max. The body is pretty much fine, just that tattoo is way bigger than you have drawn it to be. You're missing one sholder plate and the other one has a weird shape that tries to resemble the old ingame model, but same time has nothing in common. The belts on her chest are a bit bigger and bit lower and have a silver (skull like? idk) shape locking them at the center.
I mean I know you'll probly ignore me or people will hate me, but that's pretty much it.