The final nail in the coffin, as far as the consequences of superhuman actions goes, when it comes to implementing the Superhuman Registration Act could be the Hulk going on a rampage. In fact, in the comic books, the Hulk's rampage in Las Vegas (which resulted in the deaths of 26 people) was one of the main catalysts for the implementation of the act - the others being things like an attack on Manhattan in reprisal for Nick Fury's "Secret War" and anti-mutant hysteria caused by extremist groups, which was in turn caused a by some of the remaining mutants after the events of "M-Day". A Hulk rampage would be great for a number of reasons - it could cause a divide between him and some other heroes in preparation for Civil War, it could be the spark required to set a World War Hulk movie in motion and, of course, it could be the main trigger for the Superhero Registration Act to come in to play.
