I feel like Kang Woojin isn't as bad as everyone is making him out to be. It seems that he didn't know about his grandfather's threats so he just saw it as Lim Haegyung and his brother ghosting him for no reason. They were like Kang Woojin's only friends so being ghosted by them probably hurt him really bad. Then when he sees Jung Wook using Lim Haegyung so he exposed Jung Wook. He chose to hurt the person (Jung Wook) who was using the person (Lim Haegyung) who hurt him.
I feel like Kang Woojin isn't as bad as everyone is making him out to be. It seems that he didn't know about his grandfather's threats so he just saw it as Lim Haegyung and his brother ghosting him for no reason. They were like Kang Woojin's only friends so being ghosted by them probably hurt him really bad. Then when he sees Jung Wook using Lim Haegyung so he exposed Jung Wook. He chose to hurt the person (Jung Wook) who was using the person (Lim Haegyung) who hurt him.