When SM Entertainment announced that Sulli has decided to leave f(x) and she will be focus on her activities as an actress, many people in the kpop world were worried about her because they(including me) thought that she has no enough acting ability to be active as an professional actress.
Well, it's true that she couldn't have proven her competitiveness as an actress since she began to act in 2005. The thing that she has not been recognized as a competitive actress for such a long time means - in the strict sense - she is not talented in it.
However, all the people's predictions on Sulli's future as an actress were wrong. Sulli is now receiving love calls from various dramas and movies. Even though she's not the type of person who really wants to maintain a hectic schedule and she accepts just a few of invitations to appear on dramas and movies, it's true she's now a much sought-after actress. Especially, it is notable that she's had a meeting with famous movie director Lee Chang Dong because he is well known as being so particular about selecting heroines for his movie.
People in the Korean entertainment world say there are two things special about Sulli.
First, she is different from the other ordinary female idols. She expresses herself very freely through her SNS and doesn't care about haters. Even though SM Entertainment has been worried about Sulli's freewheeling lifestyle, people in the entertainment world, especially those who are in the film industry really like it because they think such a mindset is essential for artists.
Second, Sulli has a mysterious appeal. She sometimes looks very pure and innocent, but sometimes looks very sexy and louche. One of the most important requirements to become a competitive actress is the diversity of one's image. People in the film industry prefer an actress who has a variety of images because she can play various different characters. And the image of an actress sometimes is much more important than her acting ability because all the competent directors know how to devise simple but effective solutions to her lack of acting ability.(Adjusting the length of lines of dialogue, using camerawork, etc)