Vinland Saga
The son of Thors, a famous warrior on the Jomsvikings. He became part of Askeladd’s band after the latter killed his father in order to avenge him. He cared for his revenge and nothing else, doing missions for Askeladd so he could duel and kill him. Although he was given dozens of chances, he never came close to killing Askeladd.
He completely changed after Askeladd was killed by Canute in front of him. For a time he lived in slavery, emotionally dead and caring for nothing, this changed when he met Jorn.