Why is the villain scary? Because he stays calm. There are very few instances where Jang Chen lost his cool, but the truth is that he collected that anger and exerted that anger while killing his foes.
The film feels even better when we get to know it's a real life story about the gangs back in 2002–03 and how police somehow arrested these vicious MFs. The world building was good and Villain came with nothing but a desire to expand as quickly as possible.
The film's climax was good, action keeps getting better and the final battle just keep you on the edge of the seats.