My question was if there is a feeling of dislike from Korean aircrew against expat, so that many will not pass the exams in the sim or line check on purpose.
5 years ago, yes. Even 3 years ago, perhaps so. But these days, it's a different kettle of fish with all screenings sims audited by expat QA crew. If you fail the sim these days, I would say the feeling of dislike from Korean aircrew is the least of your worries.