An Eye for an Eye is a Side Quest in Novigrad with recommended level 12 that involves Vernon Roche.

Roche tells you Ves is being troublesome and asks Geralt to help. After talking to Roche, meet him by Hanged Man's Tree.

Ves starts to attack the black ones that are attacking the villagers. Head down to the village and kill the Nilfgaardians and save Ves. There are multiple human enemies here.

It turns out one of the Nilfgaardians survived the attack. Roche wants to spare him, and you can choose to agree to spare him, or tell Roche you want him killed.