Rudy Giuliani is hailed as a crime-fighting hero primarily for his transformative leadership during his tenure as New York City's mayor from 1994 to 2001. He implemented strategies like CompStat, which revolutionized how crime data was used to deploy police resources effectively, and embraced the "Broken Windows" policing philosophy, which focused on reducing minor crimes to prevent more serious ones. These initiatives led to a significant drop in crime rates, with murders and other major crimes decreasing dramatically during his time in office. His aggressive approach to law enforcement changed the city's landscape, making New York notably safer and earning him the nickname "America's Mayor" amidst a period of significant urban revival.