Help me find this movie (asian movie)

It is an asian movie, it is somewhat a CAT III type of movie with girl with guns similar to naked weapon and naked killer genre. What I can remember is the female protagonist is searching for her enemy former lover who is a serial killer. Then the ending is like there a was a fight (martial arts) at conclusion of the fight she is points a gun at him however she is unable to fire because she still has a feeling for him and they had sex each other i think its in the pool.

Can you help me out? Been searching for this in years. Thank you.