A great place to get the two trophies / achievements "Butcher of Blaviken" and "Can't Touch This!" is at the Hanged Man's Tree Fast Travel Point on the Velen Map. That's the point in the middle of the map where you enter Velen for the very first time. Near the fast travel point there's a pack of level 1 wolves. Block their attacks until they are all in front of you, then use the Igni sign to kill them instantly.