He is 'seeking revenge for' his father's murder. [=he wants to harm the person who killed his father]
He swore to 'take (his) revenge on' his enemies. [=to harm his enemies]
The bombing was 'in revenge for' the assassination of their leader.
(..) upon attacking my father's kingdom? That they have gathered together to attack Wessex? There is no doubt in my mind. These are the sons of Ragnar Lothbrok. They want revenge for the death of their father. They killed Aelle. But they know your father was complicit in his death. (..)2017 TvShow: Vikings Title: On the Eve Season: 4 Episode 19
(..) Do you understand that? You are about to receive a great heathen army. AETHELWULF: They are here. The great heathen army come to revenge the death of Ragnar Lothbrok. My Lord Bishop, let us go to war! BISHOP: God help us! I don't think he can. Ragnar! (..)2017 TvShow: Vikings Title: On the Eve Season: 4 Episode 19