In Blaviken, Geralt slew Renfri's bandits, as well as Renfri herself, in order to save the lives of innocent villagers. However, to the general populace, it looked like Geralt attacked them for no reason as no one knew of Renfri's plans.
|A townswoman||"The Butcher of Blaviken's in town. If you see him, run!!"|
Also, if Geralt chooses to speak with the guards:
|Guard||"I know we needed a witcher to kill the sewer beast...but the Butcher of Blaviken?"|
|Geralt||"What's the problem?"|
|Guard||"I know who you are. The city guards are watching you. I'll hear of no humans being slain in this town."|
|Geralt||"You'd hardly be the first to know."|
|Guard||"Witty...What you want?"|
In the conversation with Toruviel at the Scoia'tael command post, she mentions to Geralt that he is the Butcher of Blaviken and that he "plowed Renfri before [he] killed her".
During the prologue as you enter the monastery if you strike Arthur Tailles as he rolls on the ground after he will say "Stinking murderer - I remember Blaviken"
When you meet the Philip Strenger in the Witcher 3 he introduces himself by saying "blobtits call me the Bloody Baron", to which Geralt replies, "Geralt of Rivia. Blobtits call me the Butcher of Blaviken".
If Geralt chooses to spare Gaetan, he mentions his past as the "Butcher of Blaviken" and that sometimes "heads just roll", indicating that he neither absolves nor condemns the other witcher for what he did.