Bit of a tricky one, this. Oh no, not the combat - the ehtical issues.
The Witcher 3: Crime and Punishment
This one can be a bit difficult to trigger, as you have to track down a man chained to some rocks in a desolate stretch of cliff-lined coats. He's located borth of the village of Rogne on Ard Skellig; you can sail there from the Ancient Crypt signpost, if you're unlocked that - just head around the coast to the east a bit to spot the icon.
Approach the scene and the young man explains that he's been framed for murder. You can elect to set him free - if you don't, you'll fail the quest.
Finish off the quest by visiting Rogne and looking for a group of arguing villages just north of the town centre. There's a little girl there who turns out to be the prisoner's sister. You can tell her you have freed her brother or say she's learned her lesson. The quest then resolves.