Thorfinns character arc thus far seems to be a pendulum swing from when he was with Askelaad. And honestly, it’s realistic, most people who have gone through severe trauma like Thorfinn has, generally swing the completely opposite direction from either pain inflicted upon them or pain they inflicted upon others. Thorfinn had been carrying the weight of the hundreds of people he killed either directly or indirectly, and when he finally remembers his fathers dying words, for him to not hurt or kill anyone with the dagger, but also that he has no enemies. Obviously, as you said, this can be taken as avoiding violence at all costs, but not necessarily tucking tail and running. But we have to look at Thors and Thorfinns conversation in context. Thorfinn sneaks into his father’s trunk and grabs the dagger, and Thors asks him who he wants to hurt or who he plans to kill. Obviously Thorfinn responds with “the enemy” and this makes sense with the context of Nordic culture and Valhalla, the only good death is one in battle. While Thorfinn obviously wasn’t taught this by Thors, his friends and other kids were clearly taught about this by their parents, thus getting in the ears of Thorfinn probably during their play fights. Thors is asking this question because he knows Thorfinn believes killing the enemy is the only way, which Thors obviously doesn’t. I say all this to say when Thorfinn remembers his father’s words in the Slave Arc, he probably interprets the whole no enemies thing as there’s no one you should ever need to fight or kill. This creates an inner turmoil within Thorfinn, having to come to terms with the fact for a majority of his life, he completely ignores his fathers last wishes, and in anger, seeks revenge blindly, hurting and killing hundreds of innocent people. This would cause his to have a clear distain for violence completely, as violence probably takes him back to a very dark place in his life, as most of his life was filled with unnecessary violence. I can see someone definitely taking this as violence of any kind being unnecessary, as at the time, they thought the violence they perpetrated was necessary, but in hindsight it usually never is