this movie is funny because it's ridiculous

I think you have the impression that all handguns have the ability to "instant-kill" or "knock back" a person-- this is not true. Some really pack such a punch that whichever part of the body you hit the target will be knocked back, others only do "localized" damage unless you successfully aim at the heart/ head.

And in any case, an instinctive/ reactive movement by the target might hurt the hostage.

The knife can still kill with less than inches of movement. A headshot is incredibly risky. This isn't a video game. Well, it is a movie... but, you have to take into account that the world is real to the character and a headshot is incredibly risky in that situation.

The ricochet bullet kill was pretty ridiculous, but, thankfully, I think that was the most far fetched part of all of the action sequences. The swinging of a block of concrete was not that ridiculous. Pang grew up fighting all his life and most of what he survived with was not skill, but aggressiveness, willpower, and adrenaline. He was pissed hearing the girl getting kicked--that worked him up well enough to hit a guy in the face with a block of concrete. Not that crazy considering the popular real-life story of a grandmother lifting up a car to save her grandchild.

But, the characters are all quite unreasonable. I found it hard to believe that Pang, who seemed to grow up with the philosophy that you have to take care of yourself, would risk his life by going back to look for the girl. I thought he was just going to leave her at the doctor's and go to the boat by himself at first, because that's what you'd expect an assassin who has known to look out for himself all his life would have done.

The cops were all horrible at logically thinking things through and also horrible at talking things out and expressing themselves. Every cop in the movie was pathetic. But, I guess that's believable.

The girl was believable--since she doesn't have much background aside from trauma after trauma (violent and otherwise). She can do whatever she wanted and she'd still be believable with that background.

I guess you can only rationalize Pang's mistakes with love. It wasn't lust, 'cause he didn't do anything to her. Haha. But, still, a life-long fighter and assassin suddenly making such a huge mistake for a girl. Really, she would have had a pretty decent life if he left her and she was brought to the hospital... and either ended up staying in Hong Kong or being deported to Taiwan (she had a Taiwanese accent). I'm fairly sure HK and Taiwan have decent enough social service programs to help her. Unless, of course, HK policy is to just deport people to SE Asia... then you gotta worry about the slave trade (which sucks). If she was from the Mainland, she wouldn't have too much of a problem either, I think. Not sure though. I guess he saved her from the horrible life with the fat guy.

You are the one who is ridiculous!
I saw many hollywood movies in which men died because he was shot one time but in reality it's not like that
I heard about some events especially in the USA and one in russia where a man survivevd after being shot 18 times (10 bullets in the torso)!
It's not ridiculous it is a true story the man was still able to walk and talk!
Not a single shot caused a penetrating gunshot wound all were struck in the body...
Tzhe man could still walk and talk!
If you know some real competent doctors they will confirm that a human organism is able to survive pretty more deadly incredible things than you can imagine!