[@BurningCold]Okey doki.
I understand that Mister Fisticuffs was trained in the arena; doesn't really explain how he understands much in terms of any form of combat other than those with his fists, he was taught how to beat the crap out of his opponents, nothing suggests that he was taught how to use a shield, blade or hammer. 
In terms of the Argonian himself, I don't mind a brawler, it will be a nice change to be honest, but a 6'5 Argonain, who's built more than an Orc?
Nope.
Training and effort can take you far; but only as far as your genetics allow, inevitably that is the ultimate barrier that is impossible to surpass.
It'd be exceptionally rare for an Argonian to be that height, and those who are far taller than normal in ones race, tend to suffer for it - a freakishly tall human is around 6'7, and their joints pay hell for that fact, as well as other numerous issues.
Lower the height to a max of 6'2 and I'll be satisfied; otherwise keep the height and add drawbacks. 
In terms of bulk, Argonians are known for their agility and swiftness in battle - regardless of how long they train and bulk themselves up, an Orc who's done the same will always win in a contest of strength, as will a Nord, Redguard and possibly even an Imperial and Dunmer; the races typically renowned for their strength, if going from genetics alone.
Skill can make up for a lot, but an Argonaians natural speed and agility will play massively into their combat styles, regardless of what it is - I'm happy for him fight with bare fists; but be aware that you will not rely on pure strength alone against opponents in the roleplay, because training aside, you will not be physically stronger than a dremora in full plate, or a Daedroth I look forward to how you will handle certain opponents in the roleplay with a pure brawler, but equally I will keep a close eye on how realistic you write the outcomes.

On to realism as my finally point.
You have fought in the arena for years, with naught but your fists, and have only a single scar to show for it.
No.
Just.
No.
I'm aware that you said that scales regrow hiding most of the scarring, but the scales that are thick and can act as any form of real defence are those found on the Spinal column, back of the neck up around the back of the skull, as well as around the shoulder blades and the posterior and hand and feet - otherwise the scales are basically nonexistent and offer very little protection; considering that you typically fight someone by facing them, most of your scarring and wounds would occur in unscaled or small scaled areas.  
You want be someone who takes their fists to a sword fight, you are damn well gunna have a liturgy of scars to show for it; they will always have range on you, and the dumbest opponent is aware of that fact, as such you need to close the gap to fight at all, you will have gained scars in this fighting style, for there is only one path to your opponent, and that's through their weapon.

Wait till the gm has said anything on this before making any changes.