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.
(..) Do I make a quick end of them? I always thought you were one for tradition, Blackhand. Your clan was weak, and you are a traitor. I accept your challenge, if only to personally ripped the heart out of your pathetic body. You must be ready when (..)2016 Warcraft
(..) When the portal opens, when the rest of the Horde join us - All of them. - Durotan did not agree to this! And why would you care what that traitor thinks? It is time for a new leader of the Frostwolf clan. One who has the best interest of his orcs in mind. Durotan, he... has poisoned (..)2016 Warcraft