1 SUN YANG AND MACK HORTON
The rivalry started at the 2016 Rio Olympics when Australian swimmer Horton called out China's Sun for being a "drug cheat" after beating him in the 400m freestyle. The situation got worse when Horton refused to share a podium with Sun or pose for photos after coming in second in the event at last year's world championships in South Korea.
"Disrespecting me was okay, but disrespecting China was unfortunate," said Sun.
Horton received death threats and troll comments from Sun's fans on his Instagram account. With Sun serving an eight-year ban after refusing to complete a doping test, the duo are unlikely to meet again any time soon.
2 ZINEDINE ZIDANE AND MARCO MATERAZZI
With a headbutt to the chest of Italian defender Materazzi, Zidane was sent off and Italy would eventually win the 2006 World Cup final on penalties.
It would be the final act of the France midfielder's playing career.
Initial reports suggested that Materazzi told Zidane: "I prefer the whore that is your sister." But Materazzi later clarified what happened in Berlin, saying: "After the third clash, I frowned and he retorted: 'I'll give you my shirt later'. I replied that I'd rather have his sister than his shirt."
In 2010, Zidane said that he would "rather die than apologise" to Materazzi.
3 TONYA HARDING AND NANCY KERRIGAN
Imagine having a movie adapted based on you and your rival and a sports scandal that had happened in 1994. I, Tonya was that movie for Harding, revealing the sports scandal between the American figure skaters.
Before the 1994 US championships in Detroit, Kerrigan was clubbed in the knee during practice by a hitman who was hired by the former husband of Harding, who would win gold while Kerrigan was unfit to compete.
Kerrigan recovered to win silver at the 1994 Olympics. In a 2017 interview with ABC News, she revealed that she never got a direct apology from her former teammate.
4 JOSE MOURINHO AND ARSENE WENGER
During his time as Chelsea manager, Mourinho famously described then Arsenal boss Wenger as a "specialist in failure". He added that Wenger had gone eight years without winning a piece of silverware. Tensions came to a head at Stamford Bridge in 2014, when Wenger shoved Mourinho on the sidelines.
However, following Wenger's retirement announcement in 2017, the Portuguese revealed the respect he has for the Frenchman.
5 MUHAMMAD ALI AND JOE FRAZIER
Regarded as the greatest rivalry in boxing history, Ali and Frazier featured in classics such as the "Fight of the Century".
Even when previewing a bout at an ABC studio in 1974, they could not keep their hands off each other.
After both fighters retired, the animosity continued. During the opening ceremony of the 1996 Atlanta Olympics, where Ali lit the Olympic torch, Frazier said: "They should have thrown him in (the cauldron)."
6 GREG LEMOND AND LANCE ARMSTRONG
Heated feuds usually do not involve your childhood hero. Armstrong once idolised his fellow American and three-time Tour de France winner LeMond, saying: "I want to be the next Greg LeMond."
But doping accusations soured their relationship.
Eventually, Armstrong would be stripped of his seven Tour titles. LeMond believes the punishment should have been greater, saying: "he (Armstrong) should go to jail".
7 CONOR MCGREGOR AND KHABIB NURMAGOMEDOV
Since 2014, there has been nothing but hatred and bad blood between these two fighters.
Their fight at UFC 229 in 2018 only intensified the rivalry after Nurmagomedov forced McGregor to tap out. An all-out brawl ensued between the two camps when the Russian confronted McGregor's jiu-jitsu coach.
Many mixed martial arts fans expect a rematch and the Irishman said in an Instagram post: "We lost the match but won the battle. The war goes on."
8 LISA LESLIE AND LAUREN JACKSON
A rivalry that started from international play, American basketball player Leslie and Australian Jackson were already under each other's skin before they met in the Women National Basketball Association (WNBA).
Jackson introduced herself to her opposing centre with an elbow to her ribs. Leslie responded with a finger wag in Jackson's face when she was called for a foul.
At the 2000 Olympics basketball final, Jackson pulled Leslie's hair.
"She could have the hair, I will take the gold," said Leslie, who would go on to become a four-time Olympic champion.