The Killer has an appealing aesthetic, thoughtful voiceover, and strong acting, all supported by impressive visuals. However, viewed from a distance, it remains fundamentally "another" movie about a hitman, failing to make as significant an impact as something like Leon: The Professional. At its core, the story is quite simple, feeling cut short and ultimately lacking substance, though this is somewhat made up for by plenty of action sequences, explanatory dialogue, and a certain level of narrative skill. It’s slightly better than many imitators, but not as much as it probably believes. Ultimately, it provides a bit more refinement but doesn't reach the legendary status of films that initially popularized this type of story.

Source on TMDB