This Question Gets Asked A Lot So It’s A Good Idea To Clear Things Up
Armwrestling fans always look for the “armwrestler with one big arm.” However, many do not know that there are two of them! One carries the true “Hellboy” nickname, while the other has his own unique moniker.

The Original Hellboy
Matthias Schlitte, a German-born armwrestler, is the original armwrestler with the nickname “Hellboy” and is known for his massive right arm. He has the disorder Klippel–Trénaunay syndrome in his right arm, which causes immense muscle hypertrophy and growth in his right arm. It is a congenital birth defect that has given him immense armwrestling acclaim.

The Ukrainian Mutant
Oleg Zhokh, The Ukrainian Mutant, is the other well-known armwrestler with one massive arm. He was also born with a congenital birth defect of muscle hypertrophy, but in his left arm. In the armwrestling community, he is not known as the “Hellboy” although he looks like he fits the part! He is an accomplished Ukrainian armwrestler who is bouncing back from a few injuries to get back to centerstage.

It Is Important To Know Who You are Talking About
Armwrestling is a phenomenal, niche, and bombastic sport. So, when you are talking about armwrestlers with one big arm, make sure you know who is “Hellboy” (Matthias Schlitte) and who is “The Ukrainian Mutant” (Oleg Zhokh).
To make it as simple as possible: Matthias Schlitte has a massive right arm and Oleg Zhokh has a massive left arm. As of right now, these are the two armwrestlers who are outspoken about their congenital birth defect. While Jeff “Popeye” Dabe looks like he has a congenital birth defect that adds mass to his arms, he swears it is just how he was born.
Also, an important callout here is don’t confuse the pumpkin armwrestling training method, which is a training style, which Devon Larratt invented, with these two massive armwrestlers. But yes, funnily enough, Oleg and Matthias inadvertently use this method of training by proxy. However, their claim to fame is congenital birth defects, which make them incredible athletes at an armwrestling table.