1Duk-Koo Kim – after his brutal death both the referee who officiated the match and Kim's mother committed suicide
Mancini was defending his WBA lightweight title for the second time when he climbed through the ropes at Caesars. In the 13th round, Mancini unleashed a barrage of 39 straight punches. Somehow, Kim survived the round. Early in the 14th, Mancini connected with two big rights to Kim's head and the Korean dropped to the canvas. He beat the count of 10, but referee Richard Green stopped the fight. Kim was carried out of the ring by stretcher and rushed to Desert Springs Hospital. He died four days later.
This fight became famous for the aftermath: Kim's mom and the referee Richard Green committed suicide months after Kim's death. It's also said that this fight changed boxing rules and posterior fights went from 15 rounds to just 12. Mancini suffered from depression and was never the same fighter again, though he continued to box until 1993. (Source)
2Becky Zerlentes – the first woman to die in the ring
3Evander Holyfield – had his ear bite off by Mike Tyson
4Frankie Campbell – had his brain knocked off from his skull
They said that Campbell knocked down Baer in the 2nd round, and this, enraged Baer bringing Campbell to an end. While other people talk about Baer losing the 3rd and 4th round in a row, and in the 5th round he couldn't take it anymore and became enrage because Tillie "Kid" Herman -former friend and trainer of Baer who switched corners overnight - was taunting and jeering Baer. Campbell's brain was knocked off loose from his skull and was pronounced dead the next day. Baer was charged with manslaughter but later was acquitted of all charges. He would give entire earnings to Campbell's family from succeeding bouts. (Source)
5Jess Willard – the heavyweight champion who was bitten off by a contestant 60 pounds smaller
Dempsey growls there's nothing to worry about. Willard is bigger but he's not in the shape of the challenger. The Manassa Mauler' Jack Dempsey brutally beat down and dethroned reigning 6'6 champion Jess Willard in three violent rounds at the Bay View Park Arena in Toledo, Ohio. Dempsey fractured the champion's jaw in the first round and knocked him down seven times in the opening stanza alone. After two more rounds of savagery Willard's corner threw in the towel to rescue their bloody and bruised fighter. Jess Willard survives by the margin of minutes, perhaps only seconds, one of the worst beatings in the history of prize fighting.
Dempsey would go on to reign as heavyweight champion for seven straight years until he was decisioned in 1926 by Gene Tunney. (Source 1 | Source 2)
6Richard Grant – had his jaw broken when his defeated opponent hit him with no gloves on
Unfortunately the tale does not end there. James Butler continued his career after this incident but could never duplicate his earlier success. In October of 2004, Butler was arrested and charged with murdering Sam Kellerman, brother of HBO Boxing analyst Max Kellerman. He (ironically) used a hammer and set his body on fire after a dispute. Butler pled guilty in 2006 and was sentenced to 29 years in prison.
7Benny Paret – went into coma and died 10 days after a controversial fight against Fullmer
The last fight was the subject of controversies. It is theorized that one of the reasons Paret died was that he was vulnerable due to the beatings he took in his previous three fights. New York State boxing authorities were criticized for giving Paret clearance to fight just several months after he was knocked out by Gene Fullmer in his second to last bout. The actions of Paret at the weigh in before his final fight have come under scrutiny. It is alleged that Paret taunted Griffith by calling him Maricón (Spanish slang for "faggot"). Griffith wanted to fight Paret on the spot but was restrained. The referee Ruby Goldstein, a respected veteran, came under criticism for not stopping the fight sooner. Goldstein would never be the referee for a fight again as a result of the controversy from this fight.
The fight was the centerpiece of a 2005 documentary entitled Ring of Fire: The Emile Griffith Story. At the end of the documentary Griffith who has harbored guilt over the incident over the years is introduced to Paret's son. The son embraced Griffith and told him he was forgiven. (Source)
8Billy Collins Jr. – lost his vision after his opponent cheated removing padding from his gloves
9Jonathan Thaxton – had his first and most memorable knockout