[14] Their rematch took place on 26 July in a no disqualification match where the reinstated London Riots neutralised the threat of Robinson's interference and Ospreay ended Havoc's 609 day reign to become Progress Champion.

He spent the rest of the year in showcase matches against non-regular Progress wrestlers, losing to Zack Sabre Jr., Shane Strickland, Matt Riddle and Adam Cole.

On 7 May 2018, day 3 of the 2018 Super Strong Style 16 tournament, Ospreay challenged Jimmy Havoc to a match at Wembley Arena on 30 September 2018, but was forced to withdraw due to contractual obligations with New Japan Pro-Wrestling.

At Chapter 82: Unboxing Live, Ospreay and Paul Robinson defeated Aussie Open (Kyle Fletcher & Mark Davis) to become the Progress Tag Team Champions.

His second match would be against Nathan Cruz, where he would lose by DQ and thus be eliminated from the tournament but reforming the Swords of Essex when his former tag partner Paul Robinson would come out to give his support.

They held the titles for nine months and eventually became embroiled in a Best of Four match series against both The London Riots and The Alpha Males (Iestyn Rees & Charlie Garrett) for the FPW Tag Team Championship.

After failing to win the Speed King Championship from Kay Lee Ray in a co-promoted show with Combat Zone Wrestling in October, he won it a fortnight later in a Six-Way Elimination match.

On 27 August 2016 Ospreay posted a Facebook live video unveiling a new British Triangle Championship with his three Swords of Essex partners Paul Robinson, Jerry Sevanchez, and Scott Wainwright.

Black, René Duprée, and Ricochet, which put him in line for a three-way match for AJ Styles' British Heavyweight Championship, which also featured Marty Scurll, where the champion retained.

Dave Meltzer of the Wrestling Observer Newsletter reported that TNA had plans to push Ospreay, but upon finding out that he had signed to appear for NJPW relegated him to a short match on their secondary television programme.

[50] Days later, Ospreay faced Adam Brooks in the main event of a Melbourne City Wrestling show, Ballroom Brawl; defeating him to win the MCW Intercommonwealth Championship.

[59] On 20 July, Ospreay entered the 2016 Super J-Cup, defeating Consejo Mundial de Lucha Libre (CMLL) representative Titán in his first round match.

[61] On 8 October, Ospreay received his first shot at the NEVER Openweight 6-Man Tag Team Championship, but he and his Chaos stablemates Beretta and Rocky Romero were defeated by the defending champions, David Finlay, Ricochet and Satoshi Kojima.

[68] Ospreay regained the title from Scurll on 4 January 2018 at Wrestle Kingdom 12 in Tokyo Dome in a four-way match, also involving Hiromu Takahashi and Kushida.

Ospreay lost the IWGP Junior Heavyweight Championship to the winner of the tournament, Hiromu Takahashi at Dominion 6.9 in Osaka-jo Hall on 9 June in his fourth defense.

[72] At Fighting Spirit Unleashed, Ospreay entered a tournament to crown a new IWGP Junior Heavyweight Champion, due to Takahashi getting a neck injury and forcing him to vacate the belt, and lost against Marty Scurll.

At King of Pro-Wrestling (2018), Ospreay teamed with Hirooki Goto and Tomohiro Ishii in a winning effort against Suzuki-gun, represented by Minoru Suzuki, Takashi Iizuka and NEVER Openweight Champion Taichi.

Despite still being classified as a Junior Heavyweight, Ospreay entered the 2019 New Japan Cup, beating Bad Luck Fale and Lance Archer, before being eliminated by fellow Chaos member Kazuchika Okada.

With this wrestling match being awarded 5 stars, Dave Meltzer and Bryan Alvarez suggested that Will Ospreay has reached a point in his career where he is a serious contender for being the best wrestler in the world.

[137] While still signed with New Japan Pro-Wrestling, Ospreay made his surprise debut for All Elite Wrestling on the 8 June 2022 episode of Dynamite, where along with other stablemates Aaron Henare and Kyle Fletcher and Mark Davis of Aussie Open, he attacked Trent Beretta and FTR.

Soon after a singles match between both men was scheduled for AEW and NJPW's collaborative show Forbidden Door, for Ospreay's newly won IWGP United States Heavyweight Championship.

[142] On 27 July, the AEW World Trios Championship was revealed, with Ospreay and Aussie Open being named as participants in the tournament to crown the inaugural champions.

[144] Ospreay returned to AEW on the 14 June 2023 episode of Dynamite, attacking IWGP United States Heavyweight Champion Kenny Omega at the end of the show, ahead of the two men's upcoming match at Forbidden Door.

[145] On the same week's episode of Rampage, Ospreay teamed with United Empire stablemates Jeff Cobb and Kyle Fletcher, to defeat Chaos (Trent Beretta, Chuck Taylor and Rocky Romero).

[152] Ospreay's first match as an AEW contracted wrestler took place on 3 March 2024 at Revolution, defeating fellow Don Callis Family stablemate, Konosuke Takeshita.

[154][155] On the 24 April episode of Dynamite, Ospreay won a Casino Gauntlet Match, to earn the right to challenge Roderick Strong for the AEW International Championship at Double or Nothing.

[157] On the 29 May episode of Dynamite, Ospreay won his second Casino Gauntlet Match, this time to earn the right to challenge Swerve Strickland for the AEW World Championship at Forbidden Door.

On the fifth anniversary episode of Dynamite on October 2, Ospreay defended his title against Ricochet, however Konosuke Takeshita attacked both men causing the match to end in a no contest.

[181] After his match against Kota Ibushi at Wrestle Kingdom 13, Ospreay shortened his nickname to "The Assassin" and debuted a new finisher, a swinging back elbow he later named the Hidden Blade.

[188] As part of the Speaking Out movement in 2020, Ospreay was accused of blacklisting former wrestler Pollyanna after she made allegations towards his friend and tag team partner Scott Wainwright.