Taehyung wanted a revenge. If not for that person, his brother would not have committed suicide. If that person did not betray his beloved brother, there was no reason for him to end his own life. Taehyung blamed it all on that person.

Hongbin didn't ask to be the chosen one. In fact, he despised his life. Nobody loved him sincerely. They are just plain scared of him. Because he's possessed. He thought he could be freed when he met his cousin.  "Save me, Taekwoon.." - Hongbin