Who's really the greatest of all time? ESPN.com ranks 'em. Let the debate begin.
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Heavyweight
Ring career: 1985-2005. Record: 50-6-0-2 (44 KOs)
Career notes: Knocked out Trevor Berbick in the second round in November 1986 to become youngest heavyweight champion in history. … Intimidating demeanor and devastating two-fisted knockout power cowed many opponents into submission before the first bell. … Tore through heavyweight ranks until being upended by 42-1 underdog James "Buster" Douglas in 1990. … Comeback was derailed by a prison sentence for rape from 1992 to 1995. … Regained WBC heavyweight belt from Frank Bruno and WBA belt from Bruce Seldon in 1996, but lost to Evander Holyfield in November of that year. Melted down in rematch, biting both of Holyfield's ears. … Was beaten badly over eight rounds by Lennox Lewis in 2002. … Quit on his stool after six rounds in his last fight, against Kevin McBride, in 2005.
Let's go to the video: 50 Greatest: Mike Tyson

Super bantamweight, featherweight, junior lightweight
Ring career: 1993-present Record: 48-5 (34 KOs)
Career notes: Tremendously popular Mexican warrior, whose fights frequently evoke technical brawls of old. … Career defined primarily by three-fight series with compatriot Marco Antonio Barrera (W12, L12, L12) and Manny Pacquiao (W12, TKO by 10, KO by 3). … Won WBC super bantamweight title from Daniel Zaragoza in September 1997 and defended nine times. … Won WBC featherweight crown in September 2000, lost it to Barrera in June 2002, regained now-vacant title five months later. … Vacated to seize WBC 130-pound championship in February 2004, which he lost in November that year, again to Barrera. … Has lost four of his last five and is clearly in decline, but has expressed interest in having at least one more fight, for a lightweight belt.

Junior lightweight, lightweight, junior welterweight, welterweight, junior middleweight
Ring career: 1996-present. Record: 38-0 (24 KOs)
Career notes: Has greater potential than anyone on this list to rise or fall. … Blessed with tremendous natural ability, but also a skilled technician. … Won WBC 130-pound title with stoppage of Genaro Hernandez in 18th pro fight. … Added WBC lightweight belt in 2002, and junior welterweight belt in 2005. … Defeated Carlos Baldomir to become welterweight champion last year. … Won split decision against Oscar De La Hoya to annex WBC super welterweight crown. … Claims to now be retired.
Let's go to the video: 50 Greatest: Floyd Mayweather Jr.

Middleweight, light heavyweight
Ring career: 1988-present Record: 47-4-1 (32 KOs)
Career notes: Lost professional debut, as a light heavyweight, and did not fight again for 16 months. … Lost first world title challenge, against Roy Jones Jr. for vacant IBF middleweight belt, in 1993. … Drew with Segundo Mercado in second title attempt, for the same belt, in 1994, but stopped Mercado in rematch. … Made 20 successful title defenses, adding WBC and IBF titles in 2001, and WBO belt in 2004. … Lost titles to Jermain Taylor in 2005. … Retired after stepping up to light heavyweight and defeating Antonio Tarver in 2006, but will emerge from retirement to fight Winky Wright in July.

Middleweight, super middleweight, light heavyweight, heavyweight
Ring career: 1989-present Record: 50-4 (38 KOs)
Career notes: Tremendously physically gifted, with lightning reflexes and hand speed. … Won IBF middleweight title against Bernard Hopkins in 1993, then stepped up to super middleweight and dethroned champion James Toney in November 1994. … After five defenses of 168-pound crown, moved up to light heavyweight, becoming first WBC, then WBA and IBF champion. … In 2003, added a portion of the heavyweight championship when he dominated WBA titlist John Ruiz. … Through first 50 contests, only defeat was by DQ against Montell Griffin.
Bonus video: Brian Kenny on Jones' place on the list

Middleweight
Ring career: 1963-77 Record: 87-3-9-1 (59 KOs)
Career notes: Lost three times in first 19 bouts, then went undefeated over the final 81 of career. … Won world middleweight title from Nino Benvenuti in Rome in November 1970, and defended it 14 times over next seven years.

Lightweight, junior welterweight, welterweight
Ring career: 1984-2001 Record: 40-4-1-1 (17 KOs)
Career notes: Defensive master frequently left opponents flummoxed and struggling to tackle unorthodox moves. … Only definitive defeats of career were final two bouts; of other two losses, one was controversial and one, his first world title shot, against WBC champion Jose Ramirez in 1988, was considered outright robbery. … Won the title, against Greg Haugen, following year, and defeated Ramirez in a rematch. … Added WBA lightweight belt in 1990, IBF junior welterweight title in 1992 and WBC welterweight belt in 1993. … Widely believed to have beaten Julio Cesar Chavez in September 1993 bout declared a draw. … Lost close decision to Oscar De La Hoya in April 1997, and didn't hold world title again.
Let's go to the video: 50 Greatest: Pernell Whitaker

Junior featherweight, featherweight, junior lightweight
Ring career: 1989-present Record: 63-5 (42 KOs)
Career notes: Mexican brawler has evolved into masterful boxer-puncher. … Won WBO 122-pound title in March 1995, but lost title in shocker to Junior Jones in November 1996. … Regained vacant title in October 1998, and moved up to featherweight in April 2001, dominating favored Englishman Naseem Hamed. … Rebounded from stoppage defeat to Manny Pacquiao to defeat Erik Morales for second time in three-fight series and take the WBC super featherweight title. … Lost title to compatriot Juan Manuel Marquez in March.

Featherweight, junior lightweight, lightweight, junior welterweight
Ring career: 1968-95 Record: 80-8 (64 KOs)
Career notes: Classy boxer-puncher renowned for gentlemanly behavior and attitude outside ring. … Failed in first attempt at world title, falling short over 15 rounds in bid for WBA featherweight strap against Ernesto Marcel in February 1974. … Won the title on next attempt, dethroning Ruben Olivares later that year. … Defended title four times before annexing WBC 130-pound crown in January 1978; after eight defenses, moved up to lightweight, outpointing WBC champ Jim Watt in 1981. … Came up short in two epic battles with Aaron Pryor for 140-pound championship in 1982 and 1983, after which he retired, before making two short comebacks.

Featherweight, welterweight, middleweight, light heavyweight, heavyweight
Ring career: 1909-29 Record: 173-30-14 (71 KOs) and 65 no-decisions
Career notes: Won British featherweight title while only 18, and added European crown four months later. … Won world welterweight title from Jack Britton in August 1915, before losing it to, regaining it from, and losing it once more to Britton in subsequent bouts. … Fought Britton 20 times, with 12 of the bouts ending in no-decisions. … Returned to Britain to annex that country's middleweight, light heavyweight and heavyweight crowns, and challenged world light heavyweight (and European heavyweight) champion Georges Carpentier in 1922, despite weighing only 153 pounds.

Kieran Mulvaney is a freelance writer based in Washington, D.C. He covers boxing for ESPN.com, Reuters and TigerBoxing.com.

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