He was a 'traitor' who betrayed his country by selling military secrets to the enemy.
He 'turned traitor'. [=he became a traitor; he betrayed his country/friends]
She has been called a 'traitor' to the liberal party's cause.
(..) You're Sansa Stark. The eldest surviving child of Ned and Catelyn Stark. Your place is in the North. I can't marry him. You can't make me. He's a traitor. A murderer. You're not marrying Roose Bolton. No, you'll be marrying his son and heir, Ramsay. - One day he'll be Warden of the North and... (..)2015 TvShow: Game of Thrones Title: High Sparrow Season: 5 Episode 3
(..) I sent you there to collect taxes, not bodies. Lord *** refused to pay. He said the Warden of the North will always be a Stark, and he'd be damned if he kissed a traitor's boot. You left him no choice. I flayed him living, along with his wife and brother. I made his son watch. And? (..)2015 TvShow: Game of Thrones Title: High Sparrow Season: 5 Episode 3