This was such a huge letdown. There wasn't really any character development. To me it feels like they wanted to make this film more emotional than the first one. All the emotional scenes felt so forced and predictable. None of the deaths had an impact, because the characters were not built up. Also, there were way too many "villains" so to speak. You have the main threat which are the zombies, then you have the people from Hong Kong, the leader of the military, and the leader of the group. They made it seem like the military leader was going to be the main one or actually do something, but he just ended up dying in an unremarkable way. Then you have the completely overdone ending.
The first movie actually had a very good ending. The father, who lived selfishly thinking he was living that way for his daughter, actually realizes his selfish ways, then commits one last act of selflessness. Selflessness he encounters throughout the movie, such as with the husband of the pregnant wife. He also encounters selfishness with the guy who was trying to save himself and put others in harm's way, even when he was already half a zombie.
This movie tried to put a "spin" on the first movie's ending, and ended up completely ruining this movie. Overall, this movie just seemed like a very big cash grab. They got two really famous actors to lead a movie, hoping the success of the first movie, and the star power of the leading actors would make them a lot of money. If this wasn't marketed as a sequel and was a standalone movie, it would be serviceable. However, since it technically is a sequel, I advise those of you that are curious to steer clear of this movie. Just watch a detailed review of the movie to get a jist of it and keep it moving.