The scene which was hidden from the American viewers for a decade. (It was added back in for some of the versions released after 2004.)
Besson's original movie idea was more violent, and the relation between Léon and Mathilda showed much less ambiguities in the first version of the script. However, Natalie Portman's parents did not let their daughter to play that part, so the director had to rewrite the script.
You can read the version 1 script here: