Question: Danny Williams is best known for scoring an upset knockout victory against what former professional boxer who won his first 19 professional fights by knockout?

Context articles: Danny Williams (boxer)
Buster Douglas
Mike Tyson
Glen Johnson (boxer)
Damaen Kelly
Lamon Brewster
Oliver McCall
Joe Smith Jr.
Hasim Rahman
Ray Mercer

Daniel Peter "Danny" Williams (born 13 July 1973) is a British professional boxer.
 A veteran of the sport since 1995, he held the British heavyweight title twice between 2000 and 2010, and the Commonwealth heavyweight title twice between 1999 and 2006.
 Williams is best known for scoring an upset knockout victory against Mike Tyson in 2004, which earned him a mandatory WBC heavyweight title opportunity.
 In the same year, he challenged then-reigning champion Vitali Klitschko, but was stopped in eight rounds.
James "Buster" Douglas (born April 7, 1960) is an American former professional boxer who competed from 1981 to 1990, and 1996 to 1999.
 He is best known for his stunning upset of Mike Tyson on February 11, 1990 in Tokyo to win the undisputed heavyweight title.
 At the time Tyson was undefeated and considered to be the best boxer in the world, as well as one of the most feared heavyweight champions in history due to his domination of the division over the previous three years.
 The only casino to make odds for the fight (all others declining to do so as they considered the fight such a foregone conclusion) had Douglas as a 42-to-1 underdog for the fight, making his victory, in commentator Jim Lampley's words, "The biggest upset in the history of heavyweight championship fights."
 Douglas held the title for eight months and two weeks, losing on October 25, 1990 to Evander Holyfield via third-round knockout, in his only title defense.
Michael Gerard Tyson ( ; born June 30, 1966) is an American former professional boxer who competed from 1985 to 2005.
 He reigned as the undisputed world heavyweight champion and holds the record as the youngest boxer to win a heavyweight title at 20 years, 4 months and 22 days old.
 Tyson won his first 19 professional fights by knockout, 12 of them in the first round.
 He won the WBC title in 1986 after stopping Trevor Berbick in two rounds, and added the WBA and IBF titles after defeating James Smith and Tony Tucker in 1987.
 This made Tyson the first heavyweight boxer to simultaneously hold the WBA, WBC and IBF titles, and the only heavyweight to successively unify them.
Glengoffe Donovan "Glen" Johnson (born 2 January 1969) is a Jamaican professional boxer.
 A veteran of the sport for more than twenty years, he held the IBF light heavyweight title in 2004; and the IBO and "Ring" magazine light heavyweight titles from 2004 to 2005.
 Johnson is best known for his upset knockout victory over Roy Jones Jr. in 2004, as well as his iron chin and relentless pressure fighting style.
Damaen Kelly (born 18 August 1976) (also incorrectly known as "Damien Kelly") is a former professional boxer from Belfast, Northern Ireland, who represented the Ireland at the Olympics.
 Kelly fought his final professional fights in the Bantamweight division but was more noted for boxing in the Flyweight division.
 Kelly was considered to be a gifted textbook boxer but one who lacked real knockout power.
Lamon Tajuan Brewster (born June 5, 1973) is an American former professional boxer who competed from 1996 to 2010.
 He held the WBO heavyweight title from 2004 to 2006, and is best known for scoring an upset knockout victory over Wladimir Klitschko to win the vacant title.
 As an amateur, Brewster won the U.S. national championships in 1995, and a silver medal at that year's Pan American Games, both in the heavyweight division.
 Following his retirement from the sport in 2011, he became an entrepreneur and founded a consulting business.
Oliver McCall (born April 21, 1965) is an American professional boxer.
 He is best known for winning the WBC heavyweight title in 1994, after scoring an upset knockout victory over Lennox Lewis.
 The next year, he defended the title against Larry Holmes before losing it to Frank Bruno.
 McCall would also become known for an in-ring meltdown during his 1997 rematch with Lewis.
Joe Smith Jr. (born September 20, 1989) is an American professional boxer who held the regional WBC International light heavyweight title from 2016 to 2017.
 He rose to prominence in 2016 by scoring an upset knockout victory over Andrzej Fonfara, and later becoming the first boxer to score a stoppage victory over former world champion Bernard Hopkins, who retired after their fight.
Hasim Sharif Rahman (born November 7, 1972) is an American former professional boxer who competed from 1994 to 2014.
 He is a two-time world heavyweight champion, having held the unified WBC, IBF, IBO, and lineal titles in 2001; and the WBC title again from 2005 to 2006.
 Rahman first became known on the world stage in 2001 when he scored an upset knockout victory against Lennox Lewis to win the unified heavyweight championship.
 Lewis avenged the loss and regained his championship by knocking out Rahman in a rematch later that year.
 Rahman won the WBC title (initially the interim version) for a second time in 2005 by defeating Monte Barrett, after which the WBC elevated him to full champion status by the year's end.
 His reign as champion ended in 2006 via another knockout loss, this time to Oleg Maskaev in a rematch of their first fight in 1999.
Raymond Anthony "Ray" Mercer (born April 4, 1961) is an American former professional boxer, kickboxer, and mixed martial artist.
 In boxing he competed from 1989 to 2008, and held the WBO heavyweight title from 1991 to 1992.
 As an amateur he won a gold medal in the heavyweight division at the 1988 Summer Olympics.
 As a mixed martial artist, Mercer is known for scoring an upset one-punch knockout victory over former UFC heavyweight champion Tim Sylvia in 2009.