Determining the top boxer of all time is a subjective and fiercely debated topic in the world of sports. Boxing has a rich history with numerous legends who have made indelible marks on the sport. While opinions vary, several fighters are often mentioned as contenders for the title of the greatest boxer of all time:

1. Muhammad Ali (Cassius Clay): Widely regarded as one of the greatest, Muhammad Ali was known for his charisma, exceptional boxing skills, and social activism. He became a three-time world heavyweight champion and defeated formidable opponents like Sonny Liston and Joe Frazier. His epic battles and memorable quotes transcend sports.

2. Sugar Ray Robinson: Often called the pound-for-pound greatest, Sugar Ray Robinson had an astonishing 175-19-6 record with 109 knockouts. His speed, technique, and versatility earned him acclaim across weight classes.

3. Joe Louis: Known as the "Brown Bomber," Joe Louis held the world heavyweight title for a record 12 years. He defended his title 25 times and became a symbol of hope during the Great Depression and World War II.

4. Rocky Marciano: Rocky Marciano retired as the only heavyweight champion with a perfect record (49-0). His tenacity, power, and resilience made him a legendary figure in the sport.

5. Jack Johnson: Jack Johnson was the first African American to become the world heavyweight champion. His skill and defiance of racial barriers contributed to his historical significance.

6. Mike Tyson: In the late 1980s and early 1990s, Mike Tyson was a phenomenon. Known for his incredible punching power and ferocity, he became the youngest heavyweight champion in history at age 20.

7. Roberto Durán: Roberto Durán was a versatile fighter with a remarkable career spanning weight classes. His relentless style and boxing IQ earned him fame as one of the "Four Kings" of boxing in the 1980s.

8. Henry Armstrong: Henry Armstrong is the only fighter to hold world titles in three weight classes simultaneously. His incredible work rate and endurance set him apart.

The choice of the greatest boxer often depends on personal criteria, including fighting style, era, and impact on the sport. Each of these fighters made a unique contribution to the world of boxing and left a lasting legacy. Ultimately, the title of the "top boxer of all time" remains a matter of individual perspective, and the debate continues among boxing enthusiasts and historians.