Question: Roy "Pretty Boy" Shaw and Lenny "The Guv'nor" McLean were arch-rivals in what?

Context paragraphs:
Pretty Boy Floyd (film): Pretty Boy Floyd is a 1960 biographical film based on the career of the notorious 1930s outlaw Charles Arthur "Pretty Boy" Floyd.

Roy Shaw: Royston Henry Shaw (11 March 1936 – 14 July 2012), also known as Roy "Pretty Boy" Shaw, Roy "Mean Machine" Shaw and Roy West, was an English millionaire, real estate investor, author and businessman from the East End of London who was formerly a criminal and Category A prisoner.  During the 1970s–1980s, Shaw was active in the criminal underworld of London and was frequently associated with the Kray twins.  Shaw is best remembered today for his career as a fighter on the unlicensed boxing scene, becoming an arch-rival with Lenny McLean.

Aeriel Stiles: Aeriel Stiles is the first guitarist and prime songwriter from the hard rock band Pretty Boy Floyd from Hollywood, California formed in 1987.  He was replaced by guitarist Kristy Majors.  Pretty Boy Floyd are most famous for their 1989 debut album "Leather Boyz With Electric Toyz" and the two singles from it; "Rock and Roll" and "I Wanna Be With You".

Don Adams (boxer): Don "The Bull" Adams was a bare-knuckle boxer, from Waltham Cross, Hertfordshire, England.  In addition he was known as King of the Gypsies.  At least one of his fights was detected by the authorities.  Hertfordshire Constabulary reported a planned fight at Holborn Stud Farm on Sunday, 26 October 1975, between Don “The Bull” Adams and Roy “Pretty Boy” Shaw, promoted by Adams’ trainer Tom “The Bear” Brown.  Donny Adams's second for the fight was an Ex RAF policeman named Huw Rees.  This fight was banned, but must have taken place later, as Shaw was reported later to have beaten Adams.  Shaw won the bout in the first round.  Before that fight Adams had 48 bare knuckle fights and won them all.

Lenny McLean: Leonard John McLean (9 April 1949 – 28 July 1998), also known as "The Guv'nor," was an English boxer, bouncer, criminal and prisoner, author, businessman, bodyguard, enforcer, weightlifter, television presenter and actor, and has been referred to as "the hardest man in Britain".

Pretty Boy, Dirty Boy: Pretty Boy, Dirty Boy is the second studio album by Colombian singer Maluma, released on 30 October 2015, by Sony Music Latin.  Work on the album lasted three years, during which Maluma collaborated with various songwriters and producers.  "Pretty Boy, Dirty Boy" is a concept album meant to showcase the different facets of Maluma; the "Pretty Boy" side contains romantic balladry and the "Dirty Boy" consisting of reggaeton-infused seductive songs.  Four singles were released from the album, "El Tiki" and "Borró Cassette" which preceded its release and "El Perdedor" and "Sin Contrato" – all of them were successful in countries across Latin America.  In order to promote the album, Maluma embarked the Pretty Boy, Dirty Boy World Tour in 2016.

Symbiosis (A Bullet for Pretty Boy album): Symbiosis is the second studio album from A Bullet for Pretty Boy.  Razor & Tie alongside Artery Recordings released the album on July 31, 2012.  A Bullet for Pretty Boy worked with Zeuss, in the production of this album, at Planet Z Studio.

Live at the Pretty Ugly Club: Live At The Pretty Ugly Club is a live album by Pretty Boy Floyd, it is their only live album to date.  It also featured two new studio tracks.

A Bullet for Pretty Boy: A Bullet for Pretty Boy is a 1970 American feature film from director Larry Buchanan.  It stars Fabian Forte as gangster Pretty Boy Floyd and co-stars Jocelyn Lane in her final performance before retiring from acting.

Bel Ami (TV series): Bel Ami (; also known as "Pretty Boy", and "'Pretty Man", is a South Korean romantic comedy television series starring Jang Keun-suk, IU, Lee Jang-woo and Han Chae-young.  Based on the same-titled 17-volume manhwa by Chon Kye-young, it aired on KBS2 from November 20, 2013 to January 9, 2014 on Wednesdays and Thursdays at 21:55 for 16 episodes.

Supporting paragraphs: Roy Shaw Lenny McLean
Answer: boxing