Marcel Barthel

Dieter made his debut for Westside Xtreme Wrestling (wXw) in January 2009, losing to Dan Marshall.[5] Dieter's next match in wXw wouldn't be until July 2012, when he and Da Mack defeated Walter and Michael Isotov.[6] Dieter and Da Mack would go on to form a regular team, dubbing themselves Hot And Spicy. On 16 November 2013, they defeated The Autsiders (Walter and Robert Dreissker) to win the wXw World Tag Team Championship.[7] Dieter and Da Mack made 7 successful defences of the championship, defeating the likes of The Sumerian Death Squad (Tommy End and Michael Dante), Forever Hooligans (Rocky Romero and Alex Koslov) and Kazuki Hashimoto and Ryuichi Kawakami. They eventually lost the championships to Matt Striker and Trent on 15 March 2014, but won the championships back in a rematch one day later.[8] On 6 April 2014, Dieter received his first opportunity at the wXw Shotgun Championship, losing to Axel Tischer.[9] After over a combined year as wXw World Tag Team Champions, Dieter and Da Mack were defeated by French Flavour (Lucas Di Leo and Peter Fischer) on 18 October 2014, bringing their reign to an end.[10] On 22 November, he unsuccessfully challenged Walter for the wXw Unified World Wrestling Championship.[11] In February 2015, Dieter took part in the Four Nations Cup, defeating Timothy Thatcher in the final to win the tournament.[12] In March, Dieter took part in the 16 Carat Gold Tournament, defeating Zack Sabre Jr in the semi-final to advance to the final, where he lost to Tommy End.[13] In October, after a short break, Hot And Spicy teamed together once again, taking part in the 2015 World Tag Team Tournament, making it to the semi-finals where they lost to reDRagon (Kyle O'Reilly and Bobby Fish).[14] In March 2016, Dieter once again took part in the 16 Carat Gold Tournament, defeating Drew Galloway in the semi-final to advance to the final, where he lost to Zack Sabre Jr, the man he defeated to advance to the final in the previous year's tournament.[15] On 2 September, Dieter and Da Mack faced off against each other, with Da Mack coming out on top and retaining his wXw Shotgun Championship.[16] In late 2016, Dieter joined Ringkampf, and on 10 December, he defeated Marty Scurll to win the wXw Unified World Wrestling Title.[17] Dieter held the championship until March 2017, when he was defeated by Jurn Simmons.[18] In April, Dieter announced that he would be leaving wXw to pursue further opportunities outside of Germany. On 30 April, wXw held a farewell show for Dieter, titled "wXw Die Matte Ist Heilig: Farewell To Axel Dieter Jr". In his final match, he teamed with Ringkampf stablemate Walter to defeat longtime partner Da Mack and longtime rival Jurn Simmons.[19]

On 30 October, it was confirmed that Barthel, under the Axel Dieter Junior name, will return to wXw as a part of their 18th Anniversary Show on 22 December.

Representing wXw and Ringkampf, Dieter made his debut for Progress Wrestling in the United Kingdom on 15 January 2017, alongside Walter, defeating The London Riots (James Davis and Rob Lynch).[20] They returned to the promotion on 29 January 2017, losing to The South Pacific Power Trip (TK Cooper and Travis Banks).[21] They once again returned on 19 March, defeating The Hunter Brothers (Jim and Lee Hunter).[22] In his first singles match, Dieter lost to Mark Haskins.[23] On 23 April, Dieter, Walter and Timothy Thatcher unsuccessfully challenged British Strong Style (Pete Dunne, Trent Seven and Tyler Bate) in a six-man tag team match for all of British Strong Style's championships.[24]

In early 2017, after Dieter suddenly left wXw, it was rumoured that he'd signed with WWE. Dieter, under the ring name Marcel Barthel, eventually debuted for WWE's developmental territory NXT in June 2017, losing to Roderick Strong at a live event.[4] In August 2018, Barthel made his NXT television debut (taped in July) as a heel in a loss against Keith Lee. Marcel Barthel was defeated by EC3 on the NXT episode 28 November 2018. In December and January, Barthel then formed a tag team with Fabian Aichner. The duo, dubbed the "European Union", then went on to score wins on both NXT and NXT UK. Barthel and Aichner would then join forces with Walter and later on, Alexander Wolfe to form the stable Imperium. On the May 13, 2020 episode of NXT Barthel and Aichner defeated Matt Riddle and Timothy Thatcher (a substitute for Pete Dunne) to win the NXT Tag Team Championship.[25]