Fancy a punch up with the locals? Then step right up...
The Witcher 3: Fists of Fury - Velen
This quest is simple. You just need to visit four different locations and defeat the fighters in an unarmed brawl.
Jonah is in Blackbough. Walk up to the bookie to bet some money on yourself. The only advice we can give is that heavy blows seem more effective than quicker hits. A couple of knees to the face will usually leave your opponent on his back.
Once Jonah is down go to Inn at the Crossroads and have it out with Smithy, who's inside the boozer. It's a little tighter in here so you won't be able to move around much, but three or four big hits will put him out.
Now get on over to Lindenvale to go one-on-one with Fishgulper. He'll plead with you to take a dive and that's up to you. If you beat him down you'll now face the Sergeant in Crow's Perch.
You get 25 EXP for the first three fights and then another 75 for finishing off the sergeant and completing the quest.