@youkita Did you try installing and then uninstalling? (that's what worked for me)

@youkita it's sorta dumb. I actually had difficulty getting it completely off (the toolbar), and had to resort to installing it and then uninstalling it. Then it finally went away.

Same as the other people - I have two user profiles on Opera, one of them for work. Useless Amazon toolbar installed itself onto my work profile somehow (pretty certain I never asked it to), can't remove it, can't find any trace of it in my C:\ drive, doesn't show up in Extensions list, doesn't show up in Add or Remove Programs. Awesome job Opera. I really do thank you for your hard work and efforts.