Here are some other related words:
* Изменник (iz-men-nik) - This word emphasizes the act of betrayal itself.
* Перебежчик (pe-re-bezh-chik) - This word specifically refers to someone who defects to the enemy side.
* Сотрудник (so-trud-nik) - While not directly translating to "traitor," this word can be used in a derogatory way to refer to someone who collaborates with the enemy.
The best word to use depends on the context and the specific nuance you want to convey.