instigator
🇺🇸
/ˈɪnstɪɡeɪtər/
🇬🇧
/ˈɪnstɪɡeɪtə(r)/
someone who starts something, like a trouble or event
The instigator of the argument was sent out of the room.
争吵的煽动者被赶出了房间。