The performances are uniformly excellent. Jean Reno plays the tough guy role to a tee, and gives Leon extra depth and sensitivity. In limited screen time Gary Oldman is also excellent as the insane villain. But young Natalie Portman makes this movie. She brings a lively performance and has excellent chemistry with Reno. Despite her age. On the dialog front, The Professional also succeeds. There are entertaining one-liners, and all of the characters(especially Oldman's role) are well written.
The film is more about character interaction than plot. The movie sets up its premise in the opening act, but for a time is plot less, focusing entirely on its characters. It returns to a plot driven narrative about 3/5 of the way through. I always prefer plot-based stories, but The Professional's plot is still well executed.
The movie makes no attempt at realism, and despite being set in contemporary New York, feels like it is set in a completely new environment. Directot Luc Benson establishes a unique atmosphere, and brings the characters to life nicely.
The Professional has two major action sequences(one at the opening and another at the climax)and several small fights in between. Both the big battles are unique and exciting. They are also very emotionally intense due to the way the viewer cares for the characters.
The Professional is a top-notch action movie. I would heavily recommend it to fans of the genre. Anyone who appreciates strong character development would also be advised to give this film a look.