- Born: 07/08/1990 in Pinneberg, Schleswig-Holstein, West Germany
- Birthname: Marcel Barthel
- Height & Weight: 6'3", 220 Ib
- NXT Tag Team Championship – with Fabian Aichner
- wXw Unified World Wrestling Championship
- wXw World Tag Team Championship (2 times) – with Da Mack
- Mitteldeutschland Cup (2014)
- Four Nations Cup (2015)
He is a German professional wrestler currently signed to WWE, where he performs on the NXT & NXT UK brands under his real name; where he is a NXT Tag Team Champion with Fabian Aicher. Together, they are part of Walter’s stable Imperium.
Barthel is best known for his work on the independent circuit in Germany, under the ring name Axel Dieter Jr. Since debuting in March 2008, Dieter worked almost exclusively in his home country of Germany, most notably for Westside Xtreme Wrestling (wXw), with occasional appearances in the United Kingdom for Progress Wrestling. In wXw, Dieter was a two-time World Tag Team Champion and a one-time Unified World Wrestling Champion before signing with WWE in 2017.
Other Notable Achievements: EWP Tag Team Championship – with Da Mack, Great Bear Grand Championship, GSW Tag Team Championship – with Da Mack, NFC First Fighter Championship, International NCW Cruiserweight Championship, First Fighter Tournament (2010), PWF North-European Championship