Bloody Nose

Walkthrough
While at the Riften Stables, if the Dragonborn strikes up a conversation with Hofgrir, the stables owner boasts that he is the best brawler in all of Skyrim. This gives the Dragonborn an opportunity to make a wager on beating Hofgrir.

Defeat Hofgrir in an unarmed brawl
If the wager is laid, then the Dragonborn must beat the stables owner in unarmed combat. Blutige Nase