why does nidalee have such a high ban rate in korea?

Koreans don't like having to leave lane/farm to help their jungler when she invades. It's way too easy for her to invade early and get out with her high mobility.

Because she is very, very strong, only she is hard to play at the same time.

And I mean: "actually very hard to play", not "somewhat hard to play but deals enough damage for it to barely matter" like Zed.

tbh, why do you care?

You'll probably never get to play in Korea anyways without a SSN.