卖国贼

Strong, emotionally charged. Literally 'country-selling thief'. Often invoked in Chinese historical discourse around figures like Qin Hui (秦桧, who framed Yue Fei) or Wang Jingwei (汪精卫, the WWII collaborationist leader). Modern online use is also common as nationalist invective.

Highly insulting and politically charged. Don't use casually. The neutral term for a traitor in general is 叛徒 (pàntú).