I think the revenge part is that it will be exposed that all of them are adopted, meaning ...

I think the revenge part is that it will be exposed that all of them are adopted, meaning that even black haired guy is adopted and his position as a heir of company may shatter and people in company won’t vote for him to be ceo. And overall people’s attitude towards them will change. And i feel it is the main reason why the blond guy who was also assaulted decided to be on chairman side as it will at least make the black haired guy ceo. And he cares so much about black haired brother’s reputation, so he doesn’t plot against chairman like our main character.