One writer's block

It took me three months to watch the first ten episodes, but it takes only three days to watch the rest. I initially wanted to watch this because the trailer was some sort of dark story with twisted character. And yes, it does not disappoint me at all, for Bad Guy is ultimately one sick drama. Anywaaaay, basically it tells us about one young man, named Shim Gun Wook, scheming a vengeful act against one big chaebol family (think Oliver Twist against Tao Ming Tse - Gu Jyun Pyo's family), and in between those revenges, he met with a (commoners) girl who's actually trying to be a member of that family as well. Do you get it? The big chaebol family consist of (wait, lemme count) six persons, the mom and dad with four of their children. The children was introduced one by one, not necessary in sequential episodes, but in a clever way that would pull you deeper through the plot. Aish, clever director and script-writer. So, why does this young man hold a grudge against the Hong family?