No sympathy for the main characters
In the film, the two main characters from the Mainland appeared to have many bad things to say about Hong Kong, and how they were discriminated against, etc. They appeared to be totally unaware that they themselves were the villains, and that people like them were responsible for many of the problems now facing Hong Kong. I have absolutely no sympathy for them.
Lai-fu (like his brother) was willing to take the job to go down to Hong Kong to kill someone he did not even know. In the film, it was repeatedly stressed that he did not attend school and came from a poor province in China - as if that justified everything.
Dan Dan was a prostitute who made use of her multiple-entry permit to enter Hong Kong periodicallly to practice her "profession". Other than that, she bought goods and took them back to sell in her village for profit. You see, she came from the same province as Lai-fu and so her family was poor too. As in Lai-fu's case, that justified everything. Sue - Lai-fu's girlfriend shown dying in the film - was also a prostitute and came to Hong Kong for the same reason. When Sue was seriously injured, Sue's grandmother refused any offer from social workers in Hong Kong to bring her back to her relatives in China. She kept on repeating that the village from which she came was very poor.
In the film, only the cops (with the notable exception of the trigger-happy one) showed some humanity.